JP2012032908A - Method and apparatus for calculating structure or charge distribution of molecule/ion using computer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce operation amount, work and time of an operator, labor, cost and time required for calculating a stable structure of a molecule or an ion or charge distribution in the molecule or the ion by applying a quantum chemistry calculation using a computer.SOLUTION: A quantum chemistry calculation according to the invention applies a structure optimization calculation to determine a local stable structure in a molecule/ion. A charge allotted structure is obtained by allotting charge quantity to each atom by applying an electric charge balance method using a schematic structure determined based on a chemical structural formula of the molecule/ion. A structure obtained by optimizing the charge allotted structure by applying a molecular force field calculation method; and the obtained structure is used as an initial structure for applying a structure optimization calculation in the quantum chemistry calculation. The local stable structure which is thus obtained has a pseudo minimum structure or a most stable structure having a charge distribution which can be assumed as generally identical to the charge distribution in the most stable structure of the molecule/ion.

Description

  The present invention relates to a method or apparatus for calculating the structure of a molecule or polyatomic ion by a quantum chemical calculation method using a computer, and more specifically, the most stable structure of an arbitrary molecule or polyatomic ion or the most stable structure thereof. Detecting the local stable structure (hereinafter referred to as “pseudo-most stable structure”) having a charge distribution that can be regarded as almost the same as the charge distribution in the structure, and calculating the charge distribution of molecules or polyatomic ions. It relates to a method or an apparatus enabling the above. “Molecules” are atomic groups that are electrically neutral, “polyatomic ions” are atomic groups that are positively or negatively charged, and both “molecules” and “polyatomic ions” This is common in that it is an atomic group composed of various atoms bonded together.

  Due to recent improvements in computing performance of computers, molecular mechanics methods, molecular dynamics methods, or quantum chemical calculation methods such as molecular orbital methods or density functional methods can be used to estimate the physicochemical properties of various molecules and ions. It is used as an effective means for evaluating the applicability to various uses (Patent Documents 1 to 4). For example, in the field of research and development of non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries, candidate molecules and ions can be used for the purpose of searching for suitable electrolytes and electrode materials. With reference to the chemical properties, etc., ascertained from the three-dimensional structure and charge distribution determined using quantum chemical calculation methods (especially ab initio molecular orbital method or density functional method), the candidate molecules -Evaluation of the usefulness of ions as an electrolyte or electrode material is performed (Patent Documents 5 to 8, Non-Patent Document 1).

  For example, the usefulness as a cation of an ionic liquid used in a non-aqueous electrolyte secondary battery as described above for a certain ion (in this specification, unless otherwise specified, an ion is a polyatomic ion). Typically, first, a rough structure determined from the chemical structure of the ion is used as an initial structure, and a structure optimization operation by a density functional method and / or an ab initio molecular orbital method is used. By repeating the structure optimization calculation, the most stable structure (the most stable structure) is determined for the electron energy in the ion, and the charge amount (calculated electron density) of each atom in the ion in the most stable structure is determined. A distribution of electric charges assigned to each atom (partial atomic charge) is calculated (Non-Patent Document 1). If there is a positively charged atom among the atoms (excluding hydrogen atoms) for which the charge has been calculated, the atom is likely to react with oxygen radicals and is chemically unstable. The ions are evaluated as having low usefulness as electrolyte cations.

WO96 / 13785 JP 2002-260975 A JP2007-149075 JP 2003-36412 A JP 2002-63903 A JP2002-60223 JP2004-28590 JP2009-29597A

Katayama and three others, Journal of the Electrochemical Society 151 (1), A59-A63, 2004 (Journal of The Electrochemical Society, 151 (1), A59-A63, 2004) Rappe et al., The Journal of Physical Chemistry 95, 3358-3363, 1991 (J. Phys. Chem, 95, 3358-3363, 1991) Rappe and four others, Journal of the American Chemical Society 114, 10014-10035, 1992 (J. Am. Chem. Soc., 114, 10024-10035, 1992)

  As mentioned above, when estimating the charge amount (charge distribution in molecules / ions) of each atom constituting a molecule / ion, the structure optimization by quantum chemical calculation method is used. It is desirable to determine the most stable structure of the molecule / ion by repeating the conversion operation. This is because the most stable structure is the structure that the actual molecule / ion has the highest probability, and the charge distribution calculated in the most stable structure is closest to the charge distribution of the actual molecule / ion. It is possible. In general, the calculation method for obtaining the calculation result with the highest accuracy for the calculation of the electron orbital energy of molecules / ions and the determination of the most stable structure is the molecular orbital method. Therefore, in order to obtain information on the charge distribution in molecules / ions with higher accuracy, it is preferable to calculate the most stable structure and the charge amount of each atom by the molecular orbital method.

  However, the determination of the most stable structure by the molecular orbital method, in particular the ab initio molecular orbital method, has a higher calculation load than other calculation methods, requires a lot of calculation time and cost, and the most stable structure Complicated procedures and labor are required before identification. In general, in the process of determining the most stable structure of a certain molecule / ion by the ab initio molecular orbital method, that is, in the structure optimization calculation process, as already mentioned, first, the chemical structural formula of the molecule / ion Schematic structure generated based on (artificially), that is, the three-dimensional structure of the molecule / ion, such as the atomic species in the molecule / ion, the position of the atom, the position of the bond between atoms or the approximate value of the bond angle A set of parameters that determines the value is input to the computer as an initial structure. The computer solves the Schrödinger equation in the changed structure while gradually changing the input structure (ie, changing the parameters that determine the three-dimensional structure) according to a predetermined molecular orbital algorithm. The calculation of the electron orbit of the structure and the calculation of energy are repeatedly executed. And while the calculation is repeated, when the calculated energy value becomes a stable point (when the energy value becomes minimum), the structure at that time is detected as one stable structure. However, the stable structure thus found is only one local stable structure, and when another initial structure is input, another local stable structure is detected. And the local stable structure may show an energy value significantly different from the most stable structure. Therefore, in order to detect the true most stable structure, various structures are set as the initial structure, the above-described operation for detecting the local stable structure is repeated, and after all the local stable structures are detected, The structure having the lowest energy value is determined as the most stable structure. Thus, in order to detect all local stable structures, when the above calculation is repeated with trial and error, enormous time, labor and cost are required. However, the structure to be entered as the initial structure can be narrowed down to some extent by considering various knowledge and geometrical considerations of the target molecule / ion, but it is determined based on such information. In the case where there are a plurality of initial structures, considerable time, labor and cost are required until the calculation is completed. In particular, when there are conformational isomers in the target molecule / ion, the above structure optimization operation is performed for all conformational isomers, so the greater the number of conformers, The time, labor and cost required to detect the most stable structure is increased. In order to reduce the time, labor, and cost required to detect the most stable structure by such molecular orbital method, an artificially constructed rough structure is used as the initial structure, which has lower accuracy and lower computational load than molecular orbital method. In some cases, the structure optimization operation by the molecular orbital method is executed after modifying the structure so that it is close to the most stable structure by using the structure optimization operation by the density functional theory. If there are conformational isomers in the target molecule / ion, it is necessary to perform the above structural optimization calculation for all the conformational isomers. Cost.

  By the way, as in the example of the evaluation of the usefulness of the cation of the ionic liquid used in the nonaqueous electrolyte secondary battery, the charge distribution in the molecule / ion to be evaluated is the most stable structure of the molecule / ion. It is most desirable to have a charge distribution in the molecule, but if a charge distribution in the molecule / ion that can be regarded as almost the same as the charge distribution in the most stable structure is obtained, the evaluation regarding the charge distribution is performed in the most stable structure. An evaluation result similar to that obtained when the charge distribution of 1 is used will be obtained. In other words, for the purpose of arbitrary evaluation using the charge distribution in the molecule / ion, the structure of the molecule / ion to be calculated is the most stable structure or the charge distribution in the most stable structure. This means that any of the pseudo-most stable structures having a charge distribution that can be regarded as substantially the same may be used.

  In this regard, in the process of research and development by the inventor of the present invention, each atom is calculated by the charge equilibrium method (Non-patent Document 2) with respect to the three-dimensional structure roughly determined from the chemical structural formula of the molecule / ion. To the structure to which the amount of charge to be assigned (ie, the roughly determined atomic species of the molecule / ion, the position of the atom, the position of the bond between atoms and the bond angle, and the parameters that specify the three-dimensional structure, and further the charge balance (A set of parameters obtained by combining the charge amounts of each atom calculated by the method) is optimized by a molecular force field calculation method (for example, Non-Patent Document 3), and the structure thus obtained is used as an initial structure by a quantum chemical calculation method. When the structure optimization calculation process is executed, it has been found that the local stable structure obtained there is almost the most stable structure or the pseudo-stable structure as described above close to the most stable structure. In other words, as the initial structure in the structure optimization operation by the quantum chemical calculation method such as the molecular orbital method or the density functional method, each atom is defined with respect to the three-dimensional structure roughly determined from the chemical structure formula of the molecule / ion. If the structure obtained by optimizing the structure to which the charge amount calculated by the charge balance method is assigned by the molecular force field calculation method is used in the structure optimization calculation process by the quantum chemistry calculation method, It can be seen that the most stable structure or the quasi-most stable structure can be detected without the need to detect the local stable structure by performing a calculation process on a plurality of conformers, and with a significantly smaller number of operations. It was issued. Such knowledge is advantageously used to improve the method and apparatus for calculating the charge distribution in the molecule / ion by quantum chemical calculation in order to evaluate the molecule / ion in relation to the charge distribution in the molecule / ion. Will.

  Thus, a main object of the present invention is a method or apparatus for calculating a stable structure of a molecule or polyatomic ion and a charge distribution in the molecule or polyatomic ion by a quantum chemical calculation method using a computer, comprising: It is to provide a method or apparatus capable of reducing the amount of calculation of the structural optimization calculation process in the law, and saving the labor, labor, calculation cost, and time of the operator during the calculation. .

  Another object of the present invention is to reduce the degree of trial and error in setting the initial structure used in the structure optimization process in the quantum chemistry calculation method as described above. .

  Furthermore, another object of the present invention is to reduce the labor, labor, cost and / or time in the structure optimization operation process in the quantum chemical calculation method of the method or apparatus as described above. Another object of the present invention is to provide a novel configuration capable of detecting a stable structure having a charge distribution that can be regarded as being substantially the same as the charge distribution in the most stable structure of molecules / ions or the most stable structure.

  Using the above knowledge, according to the present invention, a method for determining a local stable structure of a molecule or polyatomic ion by a structure optimization operation of a quantum chemical calculation method using a computer, the molecule or polyatomic Charge allocation structure obtained by assigning the amount of charge calculated by the charge equilibrium method to each atom in a molecule or polyatomic ion in the approximate structure determined based on the chemical structure formula of the ion is used as the molecular force field calculation method Thus, there is provided a method characterized in that a first structure optimized structure obtained by structure optimization is used as an initial structure of a structure optimization operation of a quantum chemical calculation method. In the above-described configuration, the charge distribution in the molecule or polyatomic ion (that is, each in the molecule or polyatomic ion is further determined from the local stable structure determined by the structure optimization operation of the quantum chemical calculation method). (Amount of charge of atoms) may be calculated.

  In the above configuration, “structure optimization operation of quantum chemical calculation method”, as already mentioned, when a certain structure is input (when “initial structure” is given), according to a predetermined algorithm, Alternatively, the electron energy is calculated while changing a part of the structure of the polyatomic ion, and the structure that gives the minimum value of the electron energy, that is, the “local stable structure of the molecule or polyatomic ion” is searched for and detected. In addition, “schematic structure determined based on chemical structure formula of molecule or polyatomic ion” means that, for example, a molecule or polyatomic ion is constructed from the chemical structure formula of molecule or polyatomic ion by the operator. It is a schematic three-dimensional structure of a molecule or polyatomic ion determined by setting the combination of the type of atom to be performed, the position of each atom, the position and angle of each interatomic bond. The “charge assignment structure obtained by assigning the calculated charge amount” is a structure in which the charge amount of each atom calculated by the charge balance method is specified in the general structure. The “first structure-optimized structure” is a local stable structure obtained by optimizing the charge allocation structure by a molecular force field calculation method.

  In the above-described method of the present invention, in particular, the configuration to be noted is that the initial structure of the structure optimization operation of the quantum chemical calculation method is the internal structure of the molecule or polyatomic ion in the schematic structure of the molecule or polyatomic ion. The structure (first structure optimization structure) obtained by optimizing the structure of the charge assignment obtained by assigning the charge amount to each atom by the molecular force field calculation method is used. According to such a configuration, in most cases, there are usually several local stable structures calculated by the structure optimization operation of the quantum chemical calculation method using the first structure optimization structure as the initial structure. Among the local stable structures, the “stable structure” itself, which is the local stable structure that gives the lowest electron energy, is not the most stable structure, but its charge distribution (ie, within the molecule or polyatomic ion) The charge amount of each atom) is not completely coincident with the charge distribution in the most stable structure, but has a charge distribution that can be regarded as almost the same as the charge distribution in the most stable structure. The `` pseudo-most stable structure '', which is a local stable structure in which the difference from the charge distribution in the most stable structure is negligible in the evaluation of the charge distribution for molecules or polyatomic ions, , The structures available for evaluating the charge distribution within the molecule or multi-atom ions. Thus, even if the molecule or polyatomic ion of interest has a conformer, it is not necessary to search and detect local stable structures for all conformers as before, ie, quantum chemistry A structure that can be used for evaluation of charge distribution in a molecule or polyatomic ion is calculated without repeating the structure optimization operation of the calculation method by the number of conformers. Thus, according to the configuration of the present invention, the amount of calculation for obtaining the charge distribution in the molecule or polyatomic ion or the structure usable for the evaluation, the labor and time of the trial and error of the practitioner, and Labor, computation costs and time will be greatly reduced.

  In the above configuration, the structure optimization operation of the quantum chemical calculation method is specifically a structure optimization operation by the density functional method, a structure optimization operation by the molecular orbital method, or a combination thereof. Good. As is well known in this field, the density functional method is less accurate than the molecular orbital method, but it has better convergence and calculates the state of electrons with a smaller amount of computation. It is possible. Therefore, in the above-described structure optimization operation of the quantum chemical calculation method according to the present invention, preferably, first, the structure optimization operation by the density functional method is executed with the first structure optimization structure as the initial structure. A local stable structure (second structure optimized structure) is determined, and then a structure optimization operation by a molecular orbital method is performed using the second structure optimized structure as an initial structure, and the most stable structure or The local stable structure that is a pseudo-most stable structure having a charge distribution that can be considered to be substantially the same as the charge distribution in the most stable structure may be determined. According to such a configuration, rather than executing the molecular orbital method with a relatively large amount of computation from the beginning, the structure is further narrowed down to a certain extent by the density functional method, and a more highly accurate structure is calculated by the molecular orbital method. Therefore, even when the result by the molecular orbital method is finally desired, the calculation load of the structure optimization calculation is reduced. If the result structure (second structure optimization structure) obtained by the structure optimization calculation by the density functional method is sufficient for the desired charge distribution accuracy, the calculation by the molecular orbital method is not executed. May be. In addition, in the case of a relatively simple molecule or polyatomic ion, or when the first structure optimization structure is expected to be close to the most stable structure, the structure optimization operation by the density functional method is omitted. Also good.

  In the determination of the structure used as the initial structure of the structure optimization operation of the quantum chemical calculation method in the above-described method of the present invention, as described above, first, charge balance to each atom in the molecule or polyatomic ion is performed. The charge amount calculated by the method is assigned, that is, the charge amount at each atom in the general structure is designated, and the structure in which the charge amount is assigned (that is, the charge amount of each atom is The specified structure) is optimized by the molecular force field calculation method. Regarding the determination of the initial structure, in the charge balance method, electrons are added or removed from the original valence of the molecule or polyatomic ion, that is, the valence that the molecule or polyatomic ion can normally take. The charge amount can also be calculated for a radical state molecule or polyatomic ion, and thus the calculated charge amount can be assigned to each atom in the schematic structure. However, when the method of the present invention is actually executed, for a molecule or polyatomic ion in a radical state, depending on the structure optimization operation of the quantum chemical calculation method using the first structure optimization structure as the initial structure, Good results were not obtained. Therefore, in the method of the present invention, when the original valence of the molecule or polyatomic ion matches the valence of the molecule or polyatomic ion in the charge assignment structure, the quantum chemical calculation method described above is used. The local stable structure may be determined by the structure optimization calculation. Further, regarding the structure optimization of the charge assignment structure by the molecular force field calculation method, the interatomic potential function set there may be any function that is normally used in this field. In the embodiment, as the interatomic potential function, an arbitrary function considering Coulomb force or electrostatic interaction, for example, universal, dreading, compass, pcff, cvff, etc. may be used.

  By the way, the above-mentioned features of the present invention start from a schematic structure determined on the basis of a chemical structural formula of a molecule or polyatomic ion, and include a charge equilibrium method, a structure optimization operation of a molecular force field calculation method, a quantum chemical calculation method ( It can be said that the pseudo-most stable structure or the most stable structure of a molecule or polyatomic ion is determined by sequentially applying structure optimization operations of density functional method and molecular orbital method. Therefore, according to another aspect of the present invention, there is provided a method for determining a local stable structure of a molecule or polyatomic ion using a computer, which is determined based on a chemical structural formula of the molecule or polyatomic ion. A process of generating a charge assignment structure obtained by assigning a charge amount calculated by a charge equilibrium method to each atom in the molecule or polyatomic ion in a schematic structure, and the charge assignment structure by a molecular force field calculation method A process of generating a first structure optimized structure by optimization by a structure optimization operation, and determining the local stable structure by optimizing the first structure optimized structure by a structure optimization operation by a quantum chemical calculation method A process comprising the steps of:

  The method of the present invention is realized by the operation of a computer in which a program for executing a charge equilibrium method, a molecular force field calculation method, and a quantum chemistry calculation method (density functional method, molecular orbital method) is installed. Thus, according to another aspect of the present invention, an arithmetic processing for determining a local stable structure (a pseudo-most stable structure or a most stable structure) of a molecule or polyatomic ion by a structure optimization operation of a quantum chemical calculation method. An apparatus, which is obtained by assigning a charge amount calculated by a charge equilibrium method to each atom in the molecule or polyatomic ion in a schematic structure determined based on a chemical structural formula of the molecule or polyatomic ion. A first structure optimized structure obtained by optimizing a charge allocation structure obtained by a molecular force field calculation method as an initial structure of a structure optimization operation of the quantum chemical calculation method, or An arithmetic processing unit for determining a local stable structure of a molecule or polyatomic ion in a schematic structure determined on the basis of a chemical structural formula of the molecule or polyatomic ion. A means for generating a charge allocation structure obtained by allocating the amount of charge calculated by the charge balance method to an atom, and a first structure optimization by optimizing the charge allocation structure by a structure optimization operation by a molecular force field calculation method There is provided an apparatus comprising: means for generating a structure; and means for determining the local stable structure by optimizing the first structure optimized structure by a structure optimization operation using a quantum chemical calculation method . In such an apparatus, the charge distribution in the molecule or polyatomic ion may be calculated from the local stable structure determined by the structure optimization operation of the quantum chemical calculation method. Further, the interatomic potential function set in the structure optimization of the charge assignment structure by the molecular force field calculation method may be a function selected from the group consisting of universal, dreading, compass, pcff and cvff. The structure optimization operation of the chemical calculation method may include a structure optimization operation by the density functional method and / or a structure optimization operation by the molecular orbital method. Preferably, the structure optimization operation of the quantum chemistry calculation method performs the structure optimization operation by the density functional method with the first structure optimization structure as the initial structure, thereby obtaining the second structure optimization structure. And an operation for determining the local stable structure by executing a structure optimization operation by a molecular orbital method using the second structure optimized structure as an initial structure. Furthermore, even in the apparatus of the present invention, the determination of the local stable structure by the structure optimization operation of the quantum chemical calculation method is performed by the original valence of the molecule or polyatomic ion and the molecule or polyatomic ion in the charge allocation structure. It may be executed when the valence of the two matches.

  As described above, in the conventional technique, when evaluating the charge distribution in a molecule or polyatomic ion, the most stable structure is obtained by the structure optimization operation of the quantum chemical calculation method. The charge distribution within the molecule or polyatomic ion was calculated. At that time, in the search for the most stable structure by the structure optimization calculation, the initial structure was set by trial and error, experimental values, and the chemical intuition of the practitioner. The result of the calculation is not necessarily the most stable structure even if it is a single local stable structure. In general, the result of the structure optimization operation of the quantum chemical calculation method depends on the initial structure that is input. Since it can change greatly, after all the local stable structure within a certain range from a certain local stable structure is calculated, the energy of the calculated local stable structure is compared, and the most stable with the lowest energy I had to detect the structure. In particular, when the target molecule or polyatomic ion has a conformer, it was necessary to calculate the stable structure for all conformers within a certain range from a certain local stable structure. In some cases, the amount of calculation until the most stable structure is detected, the labor and effort of the practitioner, the cost and time for the calculation are enormous.

  However, in the present invention, first, in the evaluation of the charge distribution in a molecule or polyatomic ion, the most stable structure does not necessarily have to be detected, but the molecule in the most stable structure is not necessarily detected. If we know the local stable structure (pseudo-most stable structure) of a molecule or polyatomic ion with a charge distribution that can be considered to be almost the same as the charge distribution in the polyatomic ion, Accordingly, it is possible to reduce the amount of calculation required for detecting the most stable structure, the labor and effort of the practitioner, and the cost and time for calculation. In addition, as already described, in the structure optimization calculation processing of the quantum chemical calculation method, the charge equilibrium method is applied to each atom in the molecule or polyatomic ion as the initial structure in the schematic structure of the molecule or polyatomic ion. The local stable structure obtained using the structure obtained by optimizing the charge allocation structure obtained by assigning the charge amount calculated by the molecular force field calculation method in most cases is the most stable structure. Based on the knowledge that the local stable structure or the most stable structure itself of the molecule or polyatomic ion having a charge distribution that can be regarded as almost the same as the charge distribution in the molecule or polyatomic ion In addition, the labor and effort of setting the initial structure of the structure optimization operation of the quantum chemistry calculation method (including the search for conformational isomers), which was the most difficult, was greatly reduced. Fruit First, the practitioner need only set the approximate position of the atomic species in the molecule or polyatomic ion from the chemical structural formula.), Significantly reducing the number of structural optimization operations in the quantum chemical calculation method This achieves a significant reduction in computation costs and time.

  In the structure of the present invention, the structure obtained by optimizing the charge allocation structure obtained using the charge equilibrium method by the molecular force field calculation method is the initial structure of the structure optimization operation of the quantum chemistry calculation method. Then, the reason why the pseudo-stable structure or the most stable structure itself is detected by the structure optimization operation of a few quantum chemistry calculation methods is simply obtained by optimizing the structure by the molecular force field calculation method described above. This is probably because the later structure is already close to the most stable structure. That is, in general, in the formation of a three-dimensional structure of molecules or polyatomic ions, it is considered that the contribution of the action of Coulomb force between atoms is relatively large. Method, the charge amount of each atom is calculated with considerably high accuracy, and an approximately stable structure is calculated by a molecular force field calculation method considering the action of Coulomb force between atoms from the structure to which the charge amount is assigned. Therefore, it is expected that the state is already close to the most stable structure.

  Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the present invention.

FIG. 1 shows a schematic diagram of a computer device that implements the method and apparatus of the present invention. FIG. 2 is a flowchart showing the process of calculating the charge distribution in the most stable structure or pseudo-most stable structure of a molecule or polyatomic ion according to the present invention. FIG. 3 is a diagram showing a three-dimensional structure model of ions that are gradually optimized in the process of FIG. In order to clarify the structure, the display of hydrogen atoms is omitted. (A) is a schematic structure configured freehand by the practitioner, and (b) is a structure optimization performed by a simple molecular force field calculation method (clean) on the structure of (a). (C) is a structure after the structure of (b) is optimized by a molecular force field calculation method (universal) (first structure optimized structure), and (d) is (C) is a structure after the structure is optimized by a density functional method (Dmol3 from Accelrys). (E) is a structure obtained from the molecular orbital method (Gaussian manufactured by Gaussian). ) Is a structure after the structure is optimized. FIG. 4 shows (a) trimethylhexylammonium (TMHA +), (b) 1-butyl-4-methyl-pyridinium chloroaluminate (BMP +), (c) 1-ethyl- For each of 3-methylimidazolium (EMI +: 1-Etyl-3-Methyl Imidazolium), (d) 1,2-dimethyl-3-propyl imidazolium (DMPI +: 1,2-dimethyl-3-propyl Imidazolium), Schematic diagram (left figure) of the local stable structure that is the most stable structure or pseudo-most stable structure obtained by the method of the present invention, and the charge amount (black bar) of each atom obtained by the method of the present invention, It is the figure (right figure) which represented the electric charge amount (white bar) of each atom obtained by the method of the conventional method, literature value (nonpatent literature 1) (dotted line bar) in the form of a bar graph. Note that the display of hydrogen atoms is omitted in the structure diagram and the charge amount graph. FIG. 5 is a flowchart showing an example of a process for calculating the charge distribution in the most stable structure of molecules or polyatomic ions in the prior art.

DESCRIPTION OF SYMBOLS 1 ... Computer body 2 ... Computer terminal 3 ... Monitor 4 ... Keyboard, mouse (input device)

  The present invention will now be described in detail with reference to a few preferred embodiments with reference to the accompanying drawings. In the figure, the same reference numerals indicate the same parts.

Outline of the apparatus Local stable structure of a molecule or polyatomic ion having a charge distribution which can be regarded as substantially similar to the charge distribution in the molecule or polyatomic ion in the most stable structure of the molecule or polyatomic ion according to the present invention The method and apparatus capable of determining the (pseudo-most stable structure) or the most stable structure and further determining the charge distribution of molecules or polyatomic ions may be a computer apparatus 1 of the type commonly used in this field. (FIG. 1). The computer apparatus 1 is equipped with a CPU, a storage device, and an input / output device (I / O) connected to each other by a bidirectional common bus in a normal manner, and the storage device is used in the calculation of the present invention. A memory storing each program for executing a charge balance method, a molecular force field calculation method, a density functional method, and a molecular orbital method, and a work memory and a data memory used during calculation. In addition, the display and output of instructions, calculation results, and other information to the computer device 1 by the practitioner are performed through the computer terminal device 2 connected to the computer device 1. The computer terminal device 2 is provided with a monitor 3 and an input device 4 such as a keyboard and a mouse in a normal manner. When each of the programs is started, the practitioner follows the procedure of each program. In accordance with the display appearing above, various instructions and inputs can be made to the computer device 1 using the input device 4, and the calculation status and calculation results from the computer device 1 can be visually confirmed on the monitor 3. It becomes. Note that the computer device 1 and the computer terminal device 2 may be equipped with other peripheral devices (not shown) (printer for outputting results, storage device for inputting / outputting calculation conditions and calculation result information, etc.). Should be understood. When various processes or operations described below are executed using the computer apparatus 1, programs necessary for the various processes or calculations are started in a normal manner, and the practitioner can connect the computer terminal apparatus 2 to the computer terminal apparatus 2. Then, in accordance with the input procedure prepared in the program, data necessary for calculation, calculation conditions at the time of calculation, and other various settings are input, and calculation is started. Then, during or after the execution of the calculation, the calculation result can be output through the computer terminal device 2 as appropriate.

Overview of conventional methods for calculating the structure and charge distribution of molecules or ions Quantum chemical calculation for the purpose of estimating the charge distribution of a molecule or ion , that is, the charge amount of each atom constituting the molecule or ion When estimating the structure of a molecule / ion using the structure optimization calculation by the method, the actual molecule / ion is the highest as described in “Background Art” and “Problems to be Solved by the Invention” Since the structure taken with probability is the most stable structure which is the local stable structure having the lowest energy, the detection of the most stable structure of molecules and ions is most preferably attempted. However, in the past, detection of the most stable structure of molecules and ions by quantum chemical calculation methods, in particular, ab initio quantum chemistry that performs operations that do not consider experimental information about the molecules and ions of interest. In the case of the calculation method, the amount of calculation is enormous, and it requires a lot of labor, labor, calculation cost and time for the operator.

  FIG. 5 shows a typical processing process in calculating the charge distribution of molecules and ions by determining the most stable structure of molecules and ions by the structure optimization operation by the quantum chemical calculation method in the conventional technique as described above. An example is shown. Referring to the figure, in the processing process in the prior art, first, the practitioner determines the approximate structure of the molecule / ion, that is, the atomic species in the molecule / ion, from the chemical structural formula of the target molecule / ion. The information on the position of each atom, the position of the bond between atoms, the type and orientation is generally determined, and the information representing the structure is input to a computer that performs quantum chemical calculation (step 10). Then, structure optimization by the density functional method (step 20) and structure optimization by the molecular orbital method (step 30) are executed, and a local stable structure close to the general structure is determined. The first quantum chemistry calculation is preliminary structural optimization, and is intended to correct the rough structure of molecules / ions set by the practitioner to a more realistic structure. Next, based on the structure of the molecule / ion thus obtained, a search for possible conformers in the molecule / ion is performed (step 40). In searching for such conformers, plausible conformers are detected or determined based on experimental information and chemical knowledge, or using molecular dynamics or molecular dynamics techniques. All possible conformers are detected or determined. Then, the conformers are selected one by one from the conformers found in step 40 (step 45), and the structure is optimized by the density functional method for the structure of the conformers (step 50). ), Molecular orbital structure optimization (step 60) is performed, local stable structures for all conformers are first determined (step 70), and the local stable structures of all conformers are further determined. Of these, the local stable structure having the lowest energy is determined to be the most stable structure (step 80). Thus, when the most stable structure is determined, the charge amount of each atom in the structure, that is, the charge distribution is calculated (step 90).

  That is, in the processing process in the conventional technique as described above, the structure optimization calculation by the density functional method and / or the molecular orbital method can be performed for all the conformations possible in the target molecule / ion. The number of isomers will be executed, and the greater the number of conformers, the greater the amount of computation. Also, when the calculation does not converge in each structure optimization operation (steps 25, 35, 55, 65), for example, when calculating a wave function solution for one structure, or the minimum value of energy When the value does not converge in the iterative calculation when calculating the value, the calculation condition (convergence condition or input structure (initial value of the structure)) in each structure optimization calculation is changed (steps 27, 37, 57). 67) to repeat the structure optimization operation. In the processing steps in the above-described conventional technique, the initial stage input when executing the structure optimization operation is often used. When the structure is not appropriate, the calculation does not converge, or the conformational isomer that is the target of the calculation converges to a structure that is far from the local stable structure or the most stable structure. Flip, each time, time and labor such as the calculation conditions changed by trial and error is required. That is, in the above-described conventional technique, it is necessary to repeat the structure optimization operation by the quantum chemical calculation method many times before finally reaching the detection of the most stable structure of one molecule / ion. In addition, in order to reduce the number of structural optimization operations by the quantum chemistry calculation method, the initial structure to be input to the operation should be set appropriately. Or it required skillful knowledge or skill.

Overview of Calculation Method of Molecular / Ion Structure / Charge Distribution According to the Present Invention As described above, the conventional calculation method of molecular / ion structure / charge distribution has a huge amount of calculation and requires a lot of labor and labor for the operator. However, as mentioned in "Problems to be solved by the invention", the inventor of the present invention has been involved in the process of research and development in which various arithmetic experiments were attempted. As an initial structure input to the structure optimization calculation by the quantum chemical calculation method, the charge-balance method (Non-patent Document 2) is applied to the approximate structure determined from the chemical structure formula of the molecule / ion. When a structure obtained by optimizing a structure in which a charge amount is assigned to each atom (charge assignment structure) by a molecular force field calculation method (for example, Non-Patent Document 3) is used, in most cases, a density functional method is used. And / or molecular orbital method The local stable structure obtained by executing the structure optimization operation once is the most stable structure of molecules and ions, or the pseudo-stable structure, that is, almost the same as the charge distribution in the most stable structure. It has been found that the structure has a local stable structure having a charge distribution that can be regarded as being. In addition, when the structure obtained by optimizing the structure to which the charge amount is assigned by the charge balance method as described above by the molecular force field calculation method is used as the initial structure for the structure optimization operation of the quantum chemical calculation method, In the case of, the convergence of the calculation was also good.

  Therefore, in the present invention, using the above knowledge, as the initial structure of the structure optimization calculation by the quantum chemical calculation method, the charge allocation structure to which the charge amount calculated by the charge balance method as described above is assigned. A novel method using a structure obtained by optimizing the structure by molecular force field calculation is proposed. In the method of the present invention, generally speaking, after a general three-dimensional structure (schematic structure) is set from the chemical structure formula of the target molecule / ion by the operator, Then, the charge equilibrium method, the structure optimization by the molecular force field calculation method, the structure optimization by the density functional method, and / or the structure optimization by the molecular orbital method are sequentially executed, and the quasi-most stable structure or the most stable structure of the molecule / ion A local stable structure that is a structure is detected. At that time, in most cases, the structure optimization by the density functional method and the structure optimization by the molecular orbital method are performed only on the structure obtained by optimizing the charge allocation structure by the molecular force field calculation method. It's okay. In addition, as already mentioned, the reason for executing the structure optimization by the density functional method prior to the structure optimization by the molecular orbital method is that the accuracy of the calculation result is lower than that of the molecular orbital method. However, since it has good convergence and it is possible to calculate the state of electrons with a small amount of computation, the structure is further refined by the molecular orbital method after narrowing down the structure to some extent by the density functional method. This is because the calculation load of the structure optimization calculation can be reduced even if the result of the molecular orbital method is finally desired by adopting the procedure to do. Therefore, the structure optimization by the density functional method may be omitted arbitrarily. On the other hand, when the accuracy of the finally desired result is sufficient by the accuracy of the result by the density functional method, the structure optimization by the molecular orbital method may be omitted. Hereinafter, the calculation method of the structure / charge distribution of molecules or ions according to the present invention will be described in more detail.

FIG. 2 shows the process of calculating the structure / charge distribution of the molecule or ion according to the present invention . FIG. 2 shows the local stability of the most stable structure or pseudo-most stable structure of the molecule / ion by the structure optimization calculation by the quantum chemical calculation method according to the present invention. FIG. 3 schematically shows an example of the structure of a molecule obtained in the process when the structure is determined and the charge distribution of the molecule or ion is calculated. It is shown.

  Referring to FIGS. 2 and 3, in the method according to the present invention, first, as in the conventional method, the schematic three-dimensional structure of molecule / ion (schematically) Structure) (step 100) and input to the computer apparatus 1 (FIG. 1). Such a general structure is determined by parameter values such as atomic species in molecules / ions, positions of respective atoms, positions, types and orientations of bonds between atoms. It may be input using a GUI (graphical user interface) in the program. In this case, the practitioner does not directly input the parameter value in the schematic structure, but arranges atoms and bonds on the monitor 3 of the computer terminal 2 while specifying the type of each atom in the molecule / ion. (FIG. 3A). As a program used to configure the schematic structure, for example, Visualizer of Materials Studio (registered trademark) Ver. 2 or later manufactured by Accelrys can be used.

  Next, the charge balance method is executed on the schematic structure configured as described above to assign a charge amount to each atom in the structure (step 110). In short, in the charge balance method, the condition that the electronegativity of all atoms is equal in the three-dimensional structure of the input molecule / ion and the condition that the sum of charges on all atoms is equal to the charge of the whole molecule. The charge amount of each atom in the molecule / ion is calculated by solving the simultaneous equation of the charge amount of each atom obtained from (Non-patent Document 2). The specific calculation may be executed by using a charge setting method program attached to the Charge setting function attached to the Visualizer, Gaussian (registered trademark) 03 manufactured by Gaussian, Inc. Thus, when the charge balance method is executed, in the schematic structure, in addition to the parameter values that define the three-dimensional structure, a “charge allocation structure” in which the charge amount at each atom is specified is generated. Is done. In addition, before and after the application of the charge balance method, a simple molecular force field calculation method for the general structure (for example, clean of Materials Studio (registered trademark) Ver. 2 or later manufactured by Accelrys) ) Structure optimization may be applied to correct the position of atoms in the general structure, the bond angle, and the like (FIG. 3B). In the charge balance method, the original valence of the molecule / ion, that is, the valence that the molecule / ion can normally take, and the molecule / ion in the radical state in which electrons are added or removed. However, if the charge amount can be assigned, the most stable structure or pseudo-most stable structure can be obtained for the molecules and ions in the radical state when the structure optimization operation of the quantum chemical calculation method described later is executed. I couldn't. Therefore, after applying the charge balance method of step 110, it is determined whether or not the original valence of the molecule / ion and the valence of the molecule / ion in the charge assignment structure are equal, and only when they match. Subsequent processing may be executed (step 120). In the charge allocation structure, the valence of molecules / ions is set at the start of the charge equilibrium method. According to the above configuration, the valence of molecules / ions is different from the original valence of molecules / ions. In this case, it is avoided to perform the structure optimization operation of the quantum chemical calculation method in vain.

  Next, the structure optimization operation by the molecular force field calculation method is applied to the charge allocation structure formed as described above (step 130). In the molecular force field calculation method, basically, the energy in the molecule / ion is determined using a predetermined interatomic potential function with the position of each atom in the input structure, the type and orientation of the bond, and the charge amount as parameters. Is calculated. The structure optimization operation, in short, repeats the calculation of the energy in the molecule / ion while gradually changing the structure of the molecule / ion (position of each atom), and the structure that minimizes the energy (local Stable structure) is detected. In the method of the present invention, the above-described charge allocation structure is used as the first input structure, and the structure change and energy calculation processes are repeated to minimize the energy (first structure optimization structure FIG. c)) is detected. The structure optimization operation of the molecular force field calculation method may be executed in a normal mode (for example, a mode described in Non-Patent Document 3). Examples of interatomic potential functions include universal, dreading, and compass26. , Compass27, pcff, pcff30, cvff, etc., a potential function that takes into account the action of Coulomb force between atoms or electrostatic interaction may be used. The specific calculation may be executed using a program such as Forcite of Materials Studio (registered trademark) Ver. 2 or later manufactured by Accelrys, and Material Explorer manufactured by Fujitsu Limited. In the structure optimization operation, when the calculation does not converge or when it is predicted that the structure at that time is far from the most stable structure (step 135), the calculation condition (convergence condition) , The initial structure) may be changed (step 137), and the structure optimization operation may be repeated.

  Thus, when the first structure optimization structure is determined, this structure is used as it is as the initial structure, that is, the position, type, and bond type of each atom that designates the three-dimensional structure in the first structure optimization structure. Then, a structure optimization operation by the density functional method is executed using values such as position and the like (the amount of charge assigned to each atom is not used) as the initial values of the corresponding parameters (step 140). In density functional theory, the position and type of each atom in a molecule / ion, the type and position of a bond are used as input parameters to solve the Kohn-Sham equation. Energy in ions) is calculated. In short, the structure optimization operation repeats the calculation of the energy in the molecule / ion while gradually changing the structure of the molecule / ion (position of each atom), and the local stable structure that minimizes the energy. Is detected. The specific calculation is Dmol3 of Materials Studio (registered trademark) Ver. 2 or later manufactured by Accelrys, Inc. [Functional settings when using Dmol3 are, for example, GGA / PW91, GGA / BP, GGA / PBE, GGA / BYLP, GGA / BOP, GGA / VWN-BP, GGA / RPBE, GGA / HCTH, LDA / PWC, LDA / VWN, etc. may be used, and the basis functions may be selected as appropriate. ] Gaussian (registered trademark) 03 manufactured by Gaussian, Inc. [The calculation condition may be, for example, B3LYP, and the basis function may be appropriately selected. ], And may be executed using a program such as GAMESS free software. In the structure optimization calculation, when the calculation does not converge or when it is predicted that the structure at that time is far from the most stable structure (step 145), the calculation condition (convergence condition) , The initial structure) may be changed (step 147), and the structure optimization operation may be repeated. This density functional theory structure optimization operation corrects the position of each atom in the first structure-optimized structure with higher accuracy, and the resulting local stable structure becomes the second structure-optimized structure. The resulting structure (FIG. 3D).

  Next, the second structure optimization structure obtained as described above is directly used as an initial structure of the structure optimization calculation by the molecular orbital method, that is, the position, type, and the like of each atom in the second structure optimization structure. Values such as the type and position of the bond are used as initial values of the corresponding parameters in the structure optimization calculation by the molecular orbital method (step 150). The molecular orbital method here is an ab initio molecular orbital method. In brief, the molecular orbital method uses the position, type, bond type and position of each atom in the molecule / ion as input parameters. By solving the equation, the orbital function of the electrons in the molecule and the orbital energy (energy in the molecule / ion) are calculated. Then, the structure optimization calculation repeatedly calculates the energy in the molecule / ion while gradually changing the structure of the molecule / ion (position of each atom) to detect a local stable structure where the energy is minimized. The specific calculation is Gaussian (registered trademark) 03 manufactured by Gaussian, Inc. [The calculation conditions may be, for example, HF and MP2, and the basis functions may be appropriately selected. ], And may be executed using a program such as GAMESS free software. In the structure optimization calculation, when the calculation does not converge or when it is predicted that the structure at that time is far from the most stable structure (step 155), the calculation condition (convergence condition) , The initial structure) may be changed (step 157), and the structure optimization operation may be repeated. When the structure optimization calculation by the density functional method is omitted, the first structure optimization structure is used as it is as the initial structure of the structure optimization calculation by the molecular orbital method. Furthermore, the structure optimization calculation by the molecular orbital method is performed on the structure obtained by the structure optimization calculation by the molecular orbital method, and the solvent effect is further introduced. The accuracy may be improved.

  The local stable structure (FIG. 3 (e)) obtained by the structure optimization calculation by the molecular orbital method described above is the most stable structure of the target molecule / ion, as will be seen in examples described later. Or a pseudo-most stable structure having a charge distribution that can be considered to be substantially the same as the charge distribution of the most stable structure. Particularly, when the detected local stable structure is a quasi-most stable structure, according to a calculation experiment, the energy difference between the quasi-most stable structure and the most stable structure (obtained by the conventional method) is Since it is about 1 kcal / mol, the quasi-most stable structure is a structure close to the most stable structure, and considering that the error of a general experiment is about several kcal / mol, When qualitatively evaluating the charge distribution in molecules and ions, as in the example of the evaluation of the usefulness of the cation of the ionic liquid used in the non-aqueous electrolyte secondary battery described in the column, the above pseudo-stable The difference in energy between the structure and the most stable structure is substantially insignificant.

  Thus, the charge amount (partial atomic charge) of each atom in the local stable structure (that is, the most stable structure or the pseudo-most stable structure) obtained by the structure optimization operation by the molecular orbital method as described above is calculated ( Step 160). In short, the charge amount of each atom is determined by a method (Malken charge analysis) in which the Mulliken electron density calculated in the local stable structure which is the most stable structure or the pseudo-most stable structure is assigned to each atom. May be calculated. When the structure optimization calculation by the molecular orbital method is omitted, the Mulliken electron density calculated in the second structure optimization structure obtained by the structure optimization calculation by the density functional method is calculated for each atom. And the charge amount of each atom may be calculated. The specific calculation may be executed using a program such as Gaussian (registered trademark) 03 manufactured by Gaussian or free software manufactured by GAMESS.

  As described above, in the calculation method of the structure or charge distribution of the molecule or ion according to the present invention, first, the charge calculated by the charge balance method for each atom in the schematic structure of the molecule or ion of interest. A charge assignment structure with assigned quantities is generated, and the charge assignment structure is optimized by a molecular force field calculation method. This processing is performed before the structure optimization operation by the density functional method and / or the molecular orbital method for calculating the charge amount of each atom with high accuracy for the three-dimensional structure of the target molecule or ion. Using the structure optimization calculation by the molecular force field calculation method, with the amount of charge roughly calculated by the charge balance method with a relatively low calculation load assigned to each atom in the three-dimensional structure to be This corresponds to an operation of narrowing the target three-dimensional structure to some extent, that is, an operation of changing the target three-dimensional structure to a structure that is close to the most stable structure. Thereafter, the local stable structure obtained by executing the structure optimization operation by the density functional method and / or the molecular orbital method with the three-dimensional structure of the target molecule or ion close to the most stable structure as an initial structure. In most cases, it has the most stable structure or pseudo-most stable structure that can be used for evaluation of charge distribution in molecules and ions, and the charge distribution in molecules and ions in a shorter time than before. Can be calculated. In other words, in the method of the present invention, the appropriate initial structure for the structure optimization calculation by the density functional method and / or the molecular orbital method is the charge balance method and the molecular force field with a relatively small calculation load. It is set using a structure optimization operation by a calculation method, and thereby, the detection of the most stable structure or a pseudo-most stable structure close thereto is quickly achieved. In particular, in the present invention, the operation in the determination of the initial structure for the structure optimization operation by the density functional method and / or the molecular orbital method, which has been troublesome by trial and error in the past, is easy. The labor of the operator is greatly reduced. Further, in the method according to the present invention, as in the previous method illustrated in FIG. 5, the search for conformational isomers in molecules and ions and the detection of local stable structures for all searched conformers. Since it is not necessary to execute the process, the amount of calculation and the calculation time are greatly reduced as compared with the prior art.

  In order to verify the effectiveness of the present invention described above, the following calculation experiment was performed. It should be understood that the following examples illustrate the effectiveness of the present invention and do not limit the scope of the present invention.

Calculation of charge distribution of polyatomic ions In this embodiment, for example, for various polyatomic cations, the charge distribution in ions calculated according to the method of the present invention and the ion distribution calculated according to the previous method are described. The charge distribution was compared.

In the case of the method of the present invention, the processing procedure was as follows.
(1) Using the Visualizer of Materials Studio (registered trademark) Ver.2 manufactured by Accelrys Inc., specify the position, type, and position of the atoms in the ion based on the chemical structure of the ion, and outline the ion. A charge assignment structure was created by configuring the structure and assigning the amount of charge to each atom by the charge balance method using the Charge setting function attached to Visualizer.
(2) Using the Forcite of Materials Studio (registered trademark) Ver.2 manufactured by Accelrys Inc., execute the structure optimization calculation by the molecular force field calculation method for the charge allocation structure created in (1) The first structure optimized structure was generated. The interatomic potential function is universal.
(3) For the first structure optimization structure, using Accelrys Materials Studio (registered trademark) Ver.2 Dmol3, execute a structure optimization operation by density functional method, A second structure optimized structure is generated. The functional setting in the density functional method was GGA / PW91, and the basis function was DNP.
(4) Using the Gaussian (registered trademark) 03 made by Gaussian Co., Ltd., a structure optimization operation by a molecular orbital method was executed on the second structure optimized structure, thereby generating a local stable structure. The calculation method was the HF (Hartley Fock) method, and the basis function was 6-31G.
(5) Further, on the local stable structure obtained in (4), Gaussian (registered trademark) 03 manufactured by Gaussian Co., Ltd. is used to execute a structure optimization operation by a molecular orbital method in which a solvent effect is introduced. Produced a local stable structure. The calculation method was the HF (Hartley Fock) method, and the basis function was 6-31G.
(6) Using the electron density analysis function of Gaussian (registered trademark) 03, the charge amount of each atom in the most stable structure or pseudo-most stable structure obtained in (5) was calculated.

On the other hand, in the case of the conventional method, the processing procedure is as follows.
(1) Using the Visualizer of Materials Studio (registered trademark) Ver.2 manufactured by Accelrys Inc., specify the position, type, and position of the atoms in the ion based on the chemical structure of the ion, and outline the ion. Structured.
(2) The structure optimization operation by the density functional method is executed on the rough structure created in (1) using Dmol3 of Materials Studio (registered trademark) Ver.2 manufactured by Accelrys. Produced a local stable structure. The functional setting in the density functional method was GGA / PW91, and the basis function was DNP.
(3) The local stable structure obtained by (2) is further subjected to a structure optimization operation by a density functional method using Gaussian (registered trademark) 03 manufactured by Gaussian Co., Ltd. Was generated. The calculation condition in the density functional method was B3LYP / 6-31G.
(4) The molecular force field method was performed on the local stable structure obtained in (3) using CONFLEX v6.1.2 manufactured by Conflex to search for conformational isomers.
(5) For all of the conformers detected in (4), using Gaussian (registered trademark) 03 made by Gaussian, perform structure optimization by molecular orbital method to generate local stable structures did. The calculation method was the HF (Hartley Fock) method, and the basis function was 6-31G.
(6) For the local stable structure obtained in (5) for all of the conformers detected in (4), further using Gaussian (registered trademark) 03 manufactured by Gaussian, the solvent effect A local stable structure was generated by performing a structure optimization operation by the molecular orbital method with the introduction of. The calculation method was the HF (Hartley Fock) method, and the basis function was 6-31G.
(7) Of the local stable structures obtained in (6) for all of the conformers detected in (4), the structure having the minimum energy was determined as the most stable structure.
(8) Using the electron density analysis function of Gaussian (registered trademark) 03, the charge amount of each atom in the most stable structure determined in (7) was calculated.

FIG. 4 shows (a) trimethylhexylammonium (TMHA +), (b) 1-butyl-4-methyl-pyridinium chloroaluminate (BMP +), c) 1-ethyl-3-methylimidazolium (EMI +), (d) 1,2-dimethyl-3-propylimidazolium (DMPI +: 1,2-dimethyl-3-propyl) For each Imidazolium), the results obtained using the method of the present invention and the conventional method are shown. In each of (a) to (d) in the figure, the left figure shows the most stable structure or pseudo-most stable structure (however, hydrogen atoms are omitted) obtained by the method of the present invention, The right figure shows the charge amount of each atom (black bar) obtained by the method of the present invention (excluding hydrogen atoms), and the charge amount of each atom obtained by the conventional method (excluding hydrogen atoms) (white bar). ). For comparison, the charge amount (dotted bar) of each atom for the same substance described in Non-Patent Document 1 is shown. Further, the difference between the total energy value in the ions of the locally stable structure determined by the method of the present invention and the total energy value in the ions of the most stable structure determined by the conventional method is as follows for each substance. there were.
(A) 0 kcal / mol;
(B) +1.137 kcal / mol;
(C) 0 kcal / mol;
(D) +0.687 kcal / mol

When these results are referred to for each substance, they are interpreted as follows.
(A) The energy difference of the local stable structure determined by the method of the present invention is 0 kcal / mol, and the charge distribution (distribution of the charge amount of each atom) in the structure determined by the method of the present invention is conventionally The local stable structure determined by the method of the present invention is considered to be the most stable structure because it substantially matches the method and literature values.
(B) The energy difference of the local stable structure determined by the method of the present invention is about 1 kcal / mol, and considering that the error of a general experiment is about several kcal / mol, the method of the present invention It can be said that the local stable structure determined by is a local stable structure that is substantially close to the most stable structure. In addition, since the charge distribution by the method of the present invention is substantially the same as that of the conventional method and literature values, the local stable structure determined by the method of the present invention can be regarded as a pseudo-most stable structure. .
(C) The energy difference of the local stable structure determined by the method of the present invention is 0 kcal / mol, and the charge distribution in the structure determined by the method of the present invention is the atomic group (1N In the results of the method of the present invention, the order of each atom when arranged in the order of the magnitude of the charge is the same as that of the conventional method and the literature value. Matched the one. From these facts, the local stable structure determined by the method of the present invention can be regarded as a pseudo-most stable structure.
(D) The energy difference of the local stable structure determined by the method of the present invention is about 1 kcal / mol, and the error of a general experiment is about several kcal / mol. It can be said that the structure determined by is a local stable structure substantially equivalent to the most stable structure. In addition, regarding the charge distribution, there is a tendency of delocalization of charges in the atomic groups (1N to 5C) forming the resonance structure. In the result of the method of the present invention, the charge amounts are arranged in order of magnitude. The order of each atom was consistent with that of the conventional method and literature values. From these facts, the local stable structure determined by the method of the present invention can be regarded as a pseudo-most stable structure.

  Thus, in the above results, for any of the substances (a) to (d), the magnitude of the charge amount of each atom in the charge distribution in the ions obtained by the method of the present invention as a whole. Was generally consistent with the results of the conventional method and those of literature values, and the difference in total energy values was also smaller than about 1 kcal / mol. These results show that the method of the present invention enables detection of the most stable structure or pseudo-most stable structure of molecules / ions and calculation of charge distribution in the molecules / ions in the structure. In addition, it should be noted that when searching for conformers by the above-described conventional method, the number of conformers of each of the above substances is (a) 51 species, (b) 41 species, respectively. , (C) 1 type and (d) 3 types, the substances (a), (b) and (d) in the conventional method are the molecules of (6) and (7) as described above. The structure optimization operation by the orbital method was performed for all conformers, that is, the number of conformers, but in the method of the present invention, (6) and (7) The above-mentioned result was obtained by performing the structure optimization calculation by the molecular orbital method only once. That is, according to the method of the present invention, it has been shown that the amount of calculation can be greatly reduced as compared with the prior art.

  Furthermore, in the structure optimization calculation by the molecular force field calculation method (2) in the method of the present invention described above, the interatomic potential function is replaced with universal instead of dreading, compass26, compass27, pcff, pcff30, When each cvff was used to perform the same operation as described above by the method of the present invention, the finally obtained structure was almost the same as when universal was used as the interatomic potential function and was calculated. The charge distribution in the molecules and ions was also almost the same. This is not limited to universal as an interatomic potential function used in the molecular force field calculation method when generating the initial structure of the structure optimization operation of the quantum chemical calculation method in the present invention. This suggests that a potential function considering the Coulomb force action or electrostatic interaction between the atoms used can be used.

  Although the above description has been made in relation to the embodiment of the present invention, many modifications and changes can be easily made by those skilled in the art, and the present invention is limited to the embodiment exemplified above. It will be apparent that the invention is not limited and applies to various devices without departing from the inventive concept.

Claims (16)

  A method of determining a local stable structure of a molecule or polyatomic ion by a structure optimization operation of a quantum chemical calculation method using a computer, wherein the structure is determined based on a chemical structural formula of the molecule or polyatomic ion. The first structure optimization obtained by optimizing the charge assignment structure obtained by assigning the charge amount calculated by the charge equilibrium method to each atom in the molecule or polyatomic ion by the molecular force field calculation method A method wherein the structure is an initial structure of the structure optimization operation of the quantum chemical calculation method. A method for determining the local stable structure of a molecule or polyatomic ion using a computer, comprising:
A charge assignment structure obtained by assigning a charge amount calculated by a charge balance method to each atom in the molecule or polyatomic ion in a schematic structure determined based on a chemical structural formula of the molecule or polyatomic ion. Generation process,
A step of generating the first structure optimized structure by optimizing the charge allocation structure by a structure optimization operation by a molecular force field calculation method;
And determining the local stable structure by optimizing the first structure-optimized structure by a structure optimization operation by a quantum chemical calculation method.   3. The method according to claim 1, further comprising calculating a charge distribution in the molecule or polyatomic ion from the local stable structure determined by the structure optimization operation of the quantum chemical calculation method. Method.   3. The method according to claim 1 or 2, wherein the valence of the molecule or polyatomic ion matches the valence of the molecule or polyatomic ion in the charge assignment structure. Determining the local stable structure by a structure optimization operation.   3. The method according to claim 1, wherein the structure optimization operation of the quantum chemical calculation method includes a structure optimization operation by a density functional method.   3. The method according to claim 1, wherein the structure optimization operation of the quantum chemical calculation method includes a structure optimization operation by a molecular orbital method.   3. The method according to claim 1, wherein the structure optimization operation of the quantum chemical calculation method is performed by executing a structure optimization operation by a density functional method using the first structure optimization structure as an initial structure. A step of determining a second structure-optimized structure and a step of determining the local stable structure by executing a structure optimization operation by a molecular orbital method using the second structure-optimized structure as an initial structure. A method characterized by that.   The method according to claim 1 or 2, wherein the interatomic potential function set in the structure optimization of the charge assignment structure by the molecular force field calculation method is selected from the group consisting of universal, dreading, compass, pcff and cvff. A method characterized in that it is a function to be selected.   An arithmetic processing unit for determining a local stable structure of a molecule or polyatomic ion by a structure optimization operation of a quantum chemical calculation method, wherein the structure is determined based on a chemical structural formula of the molecule or polyatomic ion. A first structure-optimized structure obtained by optimizing the charge assignment structure obtained by assigning the charge amount calculated by the charge equilibrium method to each atom in the molecule or polyatomic ion by the molecular force field calculation method. An apparatus having an initial structure for a structure optimization operation of the quantum chemical calculation method. An arithmetic processing device for determining a local stable structure of a molecule or polyatomic ion,
A charge assignment structure obtained by assigning a charge amount calculated by a charge balance method to each atom in the molecule or polyatomic ion in a schematic structure determined based on a chemical structural formula of the molecule or polyatomic ion. Means for generating;
Means for optimizing the charge allocation structure by a structure optimization operation by a molecular force field calculation method to generate a first structure optimized structure;
Means for optimizing the first structure optimized structure by a structure optimization operation by a quantum chemical calculation method to determine the local stable structure.   The apparatus according to claim 9 or 10, further comprising calculating a charge distribution in the molecule or polyatomic ion from the local stable structure determined by a structure optimization operation of the quantum chemical calculation method. apparatus.   The apparatus according to claim 9 or 10, wherein the quantum chemistry calculation method when the original valence of the molecule or polyatomic ion matches the valence of the molecule or polyatomic ion in the charge assignment structure. The local stable structure is determined by a structure optimization operation.   11. The apparatus according to claim 9, wherein the structure optimization operation of the quantum chemical calculation method includes a structure optimization operation by a density functional method.   The apparatus according to claim 9 or 10, wherein the structure optimization calculation of the quantum chemical calculation method includes a structure optimization calculation by a molecular orbital method.   The apparatus according to claim 9 or 10, wherein the structure optimization operation of the quantum chemical calculation method is performed by executing a structure optimization operation by a density functional method with the first structure optimization structure as an initial structure. Including an operation for determining a second structure-optimized structure and an operation for determining the local stable structure by executing a structure optimization operation by a molecular orbital method using the second structure-optimized structure as an initial structure. A device characterized by that.   The apparatus according to claim 9 or 10, wherein the interatomic potential function set in the structure optimization of the charge assignment structure by the molecular force field calculation method is selected from the group consisting of universal, dreading, compass, pcff, and cvff. A device characterized in that it is a function to be selected.

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