KR101201867B1 - Molecular dynamics computer simulation system and method for calculation of rotational viscosity of a mixture comprising different kinds of liquid crystals - Google Patents

Abstract

을 구하기 위해 통계?분석하는 분석부를 포함한다.The present invention relates to a molecular simulation computer simulation system and its method for obtaining the rotational viscosity of different liquid crystal mixtures, and to realizing Langebin dynamics and Brown dynamics using a molecular dynamics program. A system and method for analyzing the rotation of the director vector to obtain the rotational viscosity of the liquid crystal mixture.
The present invention for achieving this object is prepared; MD process unit; And an analysis unit, which includes a preparation unit for optimizing the structure of the liquid crystal molecules as a whole, obtaining an electron density, and converting the file into a file required for molecular dynamics simulation, and modeling the molecular dynamics including force field assigning; An MD process unit for implementing Langevin dynamics simulation of the quasi-ensemble system (NVT), Langevin dynamics simulation of the isothermal isostatic ensemble system (NPT), and brown dynamics simulation of the isothermal isostatic ensemble system (NPT); And extracting the director vector of the whole liquid crystal mixture system and rotating viscosity through the extracted vector.

It includes an analysis unit that analyzes statistics and statistics to obtain.

Description

MOLECULAR DYNAMICS COMPUTER SIMULATION SYSTEM AND METHOD FOR CALCULATION OF ROTATIONAL VISCOSITY OF A MIXTURE COMPRISING DIFFERENT KINDS OF LIQUID CRYSTALS}

The present invention relates to a molecular simulation computer simulation system and method for obtaining the rotational viscosity of different liquid crystal mixtures, and more particularly, after realizing Langebin dynamics and Brown dynamics using a molecular dynamics program, Computer simulation system and method for analyzing the rotation of the director vector throughout the mixture system to obtain the rotational viscosity of the liquid crystal mixture.

The method of obtaining the rotational viscosity of the existing liquid crystal includes a rotational viscosity measuring instrument developed by Merck and a measurement method using leakage current. As a method of calculating the rotational viscosity after the measurement, a method by computer simulation of molecular dynamics (MD) is used. However, the current method of molecular dynamics, Merck Japan or Durham University, UK, is based on one molecule that is not the rotational viscosity of the liquid crystal mixture, which uses the Force Field Parameter presented in the paper. It was not one way. Since the actual LCD uses 15 to 20 kinds of different liquid crystal mixtures, it was not possible to prepare for the necessity of a method of directly obtaining the rotational viscosity of the liquid crystal mixture by the conventional method.

 In previous studies, liquid crystal molecules were approximated and calculated with ellipsoids, and even after the introduction of liquid crystal molecules using molecular dynamics, the problem of calculating the rotational viscosity of a mixture of different liquid crystal molecules could not be solved. We used many methods to average director square displacements for each molecule, but this method was difficult to apply in practice.

을 구하게 되는 일련의 과정으로, 단일계가 아닌 서로 다른 혼합액정계의 회전점도를 구하기 위한 분자동역학 컴퓨터 시뮬레이션 시스템 및 그 방법을 제공함에 있다.The present invention has been devised in view of the above problems, and the first object of the present invention is to calculate the geometry optimization and point charge using gaussian of each molecule from the initial molecular structure and pass it to AMBER MD (Molecular Dynamics). After a series of MD processes, the mean director vectors are extracted, and the rotational viscosity is obtained by substituting the slope of the mean director vectors with time for Stokes-Debye-Einstein Equation.

In a series of processes to obtain, the present invention provides a molecular dynamics computer simulation system and method for obtaining the rotational viscosity of a mixed liquid crystal system rather than a single system.

은 종래에 사용된 한 가지 분자에 대한 회전점도를 구할 수 있는 MD 방법의 문제점을 보완하여 실제 더 나은 조건을 갖는 LCD 모듈 개발시에 분자설계에 도움을 줄 수 있는 서로 다른 액정 혼합물의 회전 점도 계산을 위한 분자동역학 컴퓨터 시뮬레이션 시스템 및 그 방법을 제공함에 있다.The second object of the present invention is a rotational viscosity that can be obtained through the simulation method.

Complement the problem of the MD method, which can obtain the rotational viscosity for a single molecule used in the related art, and calculate the rotational viscosity of different liquid crystal mixtures that can assist in molecular design in developing LCD modules with better conditions. Molecular dynamics computer simulation system and method for the same.

을 구하는 통계?분석모듈을 포함한 분석부; 로 이루어진 것을 특징으로 한다. The present invention for achieving the technical problem relates to a molecular dynamics computer simulation system for the calculation of the rotational viscosity of different liquid crystal mixture, to optimize the structure of the liquid crystal molecules of different mixed liquid crystal systems and to optimize the liquid crystal molecular structure to obtain the electron density Molecular dynamics force field assignments, including modules, file converting modules that convert the optimized molecular structure into files required for molecular dynamics simulations, and force field assigning, which models the converting files appropriately for performing the MD process. A preparation unit including a modeling module; Using the sample modeled in the preparation unit, the NVT module for implementing the Langebin dynamics simulation of the canonical ensemble system, the NPT module for implementing the Langebin dynamics simulation of the isothermal isostatic ensemble system, and the brown dynamics simulation of the isothermal isostatic ensemble system. MD process unit including an NPT module to implement; And a vector analysis module for extracting the entire director vector from the liquid crystal mixture using the result data obtained through the MD process unit and a rotational viscosity using the extracted vector.

Analysis unit including a statistical analysis module to obtain; Characterized in that consisting of.

을 구하는 단계; 를 포함하는 것을 특징으로 한다.On the other hand, the present invention relates to a molecular dynamics computer simulation method for calculating the different rotational viscosity, the method comprising the steps of: (a) the preparation unit 100 to optimize the structure of the liquid crystal molecules of different liquid crystal mixture system and to obtain the electron density; (b) the preparation unit 100 converting (converting) the optimized electron density into a file required for molecular dynamics simulation through step (a); (c) the preparation unit modeling the converted file in step (b) including force field assigning to perform an MD process; (d) the MD process unit 200 implementing a Langebin dynamics simulation of the canonical ensemble system with a file modeled through the step (c); (e) the MD process unit 200 embodying a Langebin dynamics simulation of an isothermal isothermal ensemble system with a file modeled through the step (d); (f) the MD process unit 200 implementing Brownian dynamics simulation of an isothermal isothermal ensemble system with a file modeled through the step (f); (g) extracting, by the analyzer 300, the entire director vector from the liquid crystal mixture using the result data obtained through step (f); And (h) the rotational viscosity through the full director vector extracted by the analyzer 300 through the step (g).

Obtaining a; And a control unit.

는 종래에 사용된 한 가지 분자에 대한 회전점도를 구할 수 있는 MD 방법의 문제점을 보완하여 실제 더 나은 조건을 갖는 LCD 모듈 개발시에 분자설계에 도움을 줄 수 있는 효과를 가지고 있다. According to the present invention as described above, the rotational viscosity that can be obtained through the present simulation method

Complement the problem of the MD method to obtain the rotational viscosity for a single molecule used in the prior art has an effect that can help in molecular design in the development of LCD module having better conditions.

The generalized force field parameter (GAFF) is used here, which can be used for almost all organic molecules, thus ensuring the diversity of samples from which the rotational viscosity can be obtained. In addition, this method reduces the numerical error problem by extracting the mean vectors of the directors and finding the square displacement. Furthermore, the above MD series method can be implemented by automation script.

Computation time is improved by hundreds to tens of times by the recent parallel processing computer, which can help the molecular design when developing LCD module with better conditions in research and development.

1 is an overall configuration diagram of a molecular dynamics computer simulation system for calculating the rotational viscosity of different liquid crystal mixtures according to an embodiment of the present invention.
2 is a structural diagram of the component of the liquid crystal system E7.
3 is a flowchart over time of an MD process included in one embodiment of the present invention.

Specific features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings. It is to be noted that the detailed description of known functions and constructions related to the present invention is omitted when it is determined that the gist of the present invention may be unnecessarily blurred.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings.

Molecular dynamics computer simulation system and method for calculating the rotational viscosity of different liquid crystal mixtures of the present invention will be described with reference to FIGS.

1 is an overall configuration diagram conceptually showing a molecular dynamics computer simulation system for calculating the rotational viscosity of different liquid crystal mixtures according to an embodiment of the present invention. It consists of 200 and the analysis part 300.

 The preparation unit 100 optimizes the structure of the liquid crystal molecules of different liquid crystal mixtures and obtains the electron density, the liquid crystal molecule structure optimization module 110, and a file converting module for converting the optimized liquid crystal molecule structure into a file required for molecular dynamics simulation ( File Converting) 120 and a model for converting files consists of a molecular dynamics force field assignment modeling module 130, including force field assigning. This is the preparatory stage that is the foundation before entering the MD process.

In addition, the full-scale MD process unit 200 uses the modeling samples made in the preparation unit, the NVT module 210 for implementing the Langebin dynamics simulation of the canonical ensemble system, and the NPT for implementing the Langebin dynamics simulation of the isothermal isotropic ensemble system. Module 220, NPT module 230 for implementing Brown dynamic simulation of the isothermal isotropic ensemble system.

을 구하는 통계?분석모듈(320)로 구성되어 있다.
As the end of the system, the analysis unit 300 uses the vector analysis module 310 for extracting the entire director vector from the liquid crystal mixture system using the result data obtained after the simulation and the vector extracted through the above process. Rotational viscosity

It consists of a statistical analysis module 320 to obtain.

The system of each part proceeds sequentially, and the detailed description of each step is as follows.

Preparation unit 100 is a preceding part for entering the MD process of the present invention,

First, the optimization module 110 of the liquid crystal molecular structure for optimizing the structure of the liquid crystal molecules of different liquid crystal mixtures and obtaining the electron density optimizes the molecular structure based on quantum mechanical calculation using Gaussian98W or Gaussian03. The input term used here is #p hf / 6-31g (d) geom = connectivity iop (6/33 = 2,6 / 41 = 10,6 / 42 = 17) pop = mk scf = tight test. For more accurate calculations, the last term can be raised further as an option.

In addition, the file converting module 120 converting the Gaussian output file into a file required for generating a file for AMBER molecular dynamics simulation by converting the file into a file required for molecular dynamics simulation with an optimized molecular structure through the above process.

In addition, the molecular dynamics force field assignment-modeling module 130 including force field assigning is a final step performed before a full-fledged MD process, and performs modeling for the execution of the MD process with the converted molecular structure. In particular, the mixed liquid crystal system of four mixed materials E7 (5CB + 7CB + 8OCB + 5CT) is modeled by adding in the order of highest mixing ratio. Unlike conventional modeling in single system or modeling in two or more mixed liquid crystal systems, modeling in four or more mixed liquid crystal systems is now possible. The molecular structure of the mixed liquid crystal system E7 is shown in detail in FIG.

More specifically, in relation to the force field assignment, the general form of the force field of the AMBER package used in the present invention can be expressed by Equation 1.

U (R) can be expressed by Equation 1, which is basically an energy term for the distance between atoms, an energy term for angle between three atoms, an energy term for backside angle, and an energy term for intermolecular force. It consists of energy term for electrostatic force, and Langevin force field is applied by using input parameter.

However, the force field actually used in the present invention is a generalized AMBER force field (GAFF), which is different from previous AMBER force fields developed for biomolecules such as proteins and DNA. Rather, GAFF has been developed more for organic molecules, which is very suitable for liquid crystal molecules. Thus, Langevin's technique can be used to study mixed liquid crystals. However, since there is no change in U (R), which is a general force field of GAFF and the existing AMBER force field, the force field assignment modeling module 130 uses Equation 1 as it is.

The MD process unit 200 implements the molecular dynamics computer simulation in earnest and performs the MD process for each step. A flowchart of the MD process itself over time can be described in more detail with reference to FIG. 3.

Figure 3 is a flow chart of the MD process itself as a time-dependent step (NVT) to create a single system (S10), isothermal isostatic ensemble (NPT) to increase the density (S20), isothermal isostatic ensemble (NPT) of the system Equilibrium step (S30), and isothermal isostatic ensemble (NPT) to produce a step (S40).

The NVT module 210 of the MD process unit 200 implements the molecular structure that has been modeled for the MD process through the preparation unit 100 by Langevin dynamic simulation of the canonical ensemble system. To carry out. This corresponds to the step (S10) of making the Canonical Ensemble (NVT) single system of the MD process. Step S10 is an essential step to implement / perform Langebin MD for 15ns at a time of 150,000 steps in a normal ensemble (NVT) condition.

Subsequently, the NPT module 220 implements the Langebin dynamic simulation of the isothermal isostatic ensemble system, which consists mainly of increasing the density of the MD process (S20) and maintaining the equilibrium state (S30). In order to verify that the simulation is working well, it is executed in two steps. Actually, S20 and S30 can be executed successively without conceptual division. However, in order to prevent computer waste of computation time, the process is divided into steps to check the progress of the simulation.

In fact, S20 and S30 can be considered conceptually the same, but if the number and type of molecules in the mixed liquid crystal system are different, the execution time should be adjusted by observing the density change of the whole system in S20. In addition, the S30 couples the temperature-pressure more strongly to create an equilibrium. In this step, Langebin MD is performed for 5,000,000 steps for 10 ns in an isothermal-isothermal ensemble (NPT) condition.

In addition, the NPT module (Brown mechanics) 230 implements brown dynamics simulation of isothermal isostatic ensemble system, in order to induce the natural molecular behavior as much as possible by forgetting the orientation structure input by artificially modeling different liquid crystal mixing systems. As a step of giving, it corresponds to the step (S40) of producing an isothermal isothermal ensemble (NPT) of the MD process. This Brown MD is an essential step and can be implemented by minimizing temperature and pressure coupling from the outside while performing Langebin MD. In this case, the energy of the liquid crystal mixture system should be maintained theoretically, but in actual computer simulation, weak temperature and pressure coupling is performed to overcome the problem that the energy may leak out and cause the total energy to fall. This step collects data while maintaining 1,000,000 steps or 2ns.

을 구한다. 분석부(300)는 시뮬레이션이 수행된 후 나온 결과데이터를 이용하여 액정 혼합계 전체 방향자 백터를 추출하는 벡터분석모듈(310)과 상기 과정을 통해 추출된 벡터를 이용하여 회전점도

을 구하는 통계?분석모듈(320)로 구성되어 있다. And, the analysis unit 300 has the actual rotational viscosity with the data collected after the MD process is finished

. The analysis unit 300 uses the vector analysis module 310 for extracting the entire director vector from the liquid crystal mixture system using the result data obtained after the simulation and the rotational viscosity using the vector extracted through the above process.

It consists of a statistical analysis module 320 to obtain.

The vector analysis module 310 extracts the entire director vector using the simulation result data in order to analyze the molecular dynamics simulation, that is, the director fluctuation of the entire liquid crystal mixture system after the MD process is completed.

을 구한다. 이는 서로 다른 액정 혼합물의 평균방향자의 요동을 이용할 수도 있고, 서로 다른 액정 혼합물의 평균 쌍극자모멘트의 요동을 추적하여 계산하는 방법을 이용할 수도 있는 것으로, 시뮬레이션을 이용하여 얻은 데이터로 회전점도

을 구할 수 있게 된다.In addition, the statistical analysis module 320 is a rotational viscosity by using the statistical analysis of the extracted vector information using an analysis tool produced in-house through visual programming

. This method may use the fluctuations of the average directors of different liquid crystal mixtures, or may use a method of tracking and calculating the fluctuations of the average dipole moments of different liquid crystal mixtures.

Will be available.

을 계산하기 위해서는 평균제곱변위 값을 구해야하는데, 평균방향자의 제곱변위를 구하는 것으로 평균제곱변위를 구하는 것이 본 발명의 고유방법이다. 좀 더 구체적으로, 평균방향자의 제곱변위를 구하는 방법은, 일정한 시간폭 만큼의 평균방향자의 벡터값들의 제곱변위를 구하고 시작점을 임의의 시간으로 옮긴 후 다시 반복하는데 그 반복회수는 약 시간폭의 길이에 정비례하도록 한다. 그 이유는, 이 방법을 설계하는 과정에서 경험적으로 안정된 경우를 찾은 것이다. 이를 반복 회수로 나누어 평균제곱변위를 구한 후, 다시 평균제곱변위를 구하는 시간폭을 일정한 스텝씩 늘려가며 위의 계산과정을 반복한다. 그러면 평균제곱변위를 구하는 각각의 시간폭에 대하여 시간에 대한 평균제곱변위의 직선의 기울기를 최소자승법에 의하여 구하게 되는데, 각각의 결정계수값들을 함께 계산한다.Rotational viscosity

In order to calculate the mean square displacement, the mean square displacement is obtained by calculating the square displacement of the average director. More specifically, the method of calculating the square displacement of the average director takes the square displacement of the vector values of the average director by a constant time width, shifts the starting point to an arbitrary time, and repeats again. Should be directly proportional to The reason for this was to find an empirically stable case in the design of this method. After dividing this by the number of repetitions, find the mean square displacement, and then repeat the above calculation process by increasing the time width to find the mean square displacement by a certain step. Then, the slope of the straight line of the mean square displacement with respect to time is calculated by the least-squares method for each time width for which the mean square displacement is obtained.

 The rotational viscosity can be obtained by substituting the mean square displacement value of MD, average volume, and time in the rotational viscosity calculation formula. The average of 30 points is taken as the calculated value of the rotational viscosity. Here the more complex the system, the more different molecules in the system, the longer it will take to equilibrate, and in order to reduce the noise from the complex system and to obtain accurate calculations, The number of averages will also need to be corrected by empirical rules.

The slope of the straight line of the squared displacement of the mean director with respect to the time by the least square method in the self-developed analysis code The entire process of finding the solution is complete.

Here, the average of the rotational viscosity values can be obtained using Equation 2. It is derived from the Einstein relation and the Stokes-Einstein-Debye equation, and is widely used in the present invention.

는 분자동역학 모의실험을 통해 얻게 되는 액정분자 계의 방향자의 시간에 대한 평균제곱변위의 기울기이며, 부피 V와 온도 T는 각각 분자동역학 시뮬레이션과정에서 얻어진 계의 평균부피와 평균온도이고

는 볼쯔만상수이다.

Is the slope of the mean square displacement with respect to the time of the director of the liquid crystal molecular system obtained through molecular dynamics simulation, and the volume V and temperature T are the average volume and the average temperature of the system obtained during the molecular dynamics simulation, respectively.

Is Boltzmann constant.

That is, this method uses the method of obtaining the rotational viscosity using the method of calculating the squared displacement of the average director of the mixed liquid crystal composed of different liquid crystal molecules to find their average squared displacement, and then obtaining the slope of the mean squared displacement with respect to time. will be.

While the present invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. It will be appreciated by those skilled in the art that numerous changes and modifications may be made without departing from the invention. Accordingly, all such appropriate modifications and changes, and equivalents thereof, should be regarded as within the scope of the present invention.

100; Preparation section 110; Optimization Module of Liquid Crystal Molecular Structure
120; File converting module
130; Force field assignment and modeling module
200; MD process unit 210; NVT (rangebin mechanics) module
220; NPT (langebin mechanics) module 230; NPT (Brown Mechanics) Module
300; Analysis unit 310; Vector analysis module
320; statistics? Analysis module

Claims (6)

In the molecular dynamics computer simulation system for calculating the rotational viscosity,
Liquid crystal molecular structure module 110 for obtaining structures and electron densities of liquid crystal molecules of different mixed liquid crystal systems, a file converting module (File Converting) 120 for converting the structure of the liquid crystal molecules into a file for molecular dynamics simulation, and the converting A preparation unit 100 including a molecular dynamics force field assignment modeling module 130 including force field assigning for modeling a file for performing an MD process;
NVT module 210 for implementing the Langevin dynamics simulation of the quasi-ensemble system, NPT module 220 for implementing the Langebin dynamics simulation of the isothermal isotropic ensemble system, using the sample modeled by the preparation unit 100, And an MD process unit 200 including an NPT module 230 for implementing Brownian dynamic simulation of an isothermal isothermal ensemble system. And
The vector analysis module 310 extracts the entire director vector from the liquid crystal mixture using the result data obtained through the MD process unit 200, and the average direction of the mixed liquid crystals composed of different liquid crystal molecules using the extracted vector. Find the square displacement of the ruler, find their mean square displacement, and then use the method to find the slope of the mean square displacement over time.

Obtained by the analysis unit 300, including a statistical analysis module 320,
The statistical analysis module 320,
After calculating the squared displacement of the average director of the mixed liquid crystal composed of different liquid crystal molecules to obtain the average square displacement, the method of calculating the rotational viscosity using Equation 2 is used to Molecular dynamics computer simulation system for rotational viscosity calculation.
&Quot; (2) "

; Gradient of Mean Square Displacement with Time of the Director of Liquid Crystal Molecular System Obtained by Molecular Dynamics Simulation
V; Average volume obtained through molecular dynamics simulation
T; Average temperature obtained through molecular dynamics simulation

; Boltzmann constant
The method of claim 1,
The molecular dynamics force field assignment modeling module 130 is a molecular dynamics computer simulation system for calculating the rotational viscosity of different liquid crystal mixtures, characterized in that using the force field of the Generalized AMBER Force Field (GAFF).
delete In the molecular dynamics computer simulation method for calculating different rotational viscosities using a system comprising a preparation unit 100, MD process unit 200 and the analysis unit 300,
(a) obtaining, by the preparation unit 100, structures and electron densities of liquid crystal molecules of different liquid crystal mixtures;
(b) the preparation unit 100 converting (converting) the liquid crystal molecular structure of step (a) into a file required for molecular dynamics simulation;
(c) the preparation unit modeling the converted file in step (b) including force field assigning to perform an MD process;
(d) the MD process unit 200 implementing a Langebin dynamics simulation of the canonical ensemble system with a file modeled through the step (c);
(e) the MD process unit 200 embodying a Langebin dynamics simulation of an isothermal isothermal ensemble system with a file modeled through the step (d);
(f) the MD process unit 200 implementing Brownian dynamics simulation of an isothermal isothermal ensemble system with a file modeled through the step (e);
(g) extracting, by the analyzer 300, the entire director vector from the liquid crystal mixture using the result data obtained through step (f); And
(h) the analyzer 300 obtains the square displacement of the average director of the mixed liquid crystal molecules composed of different liquid crystal molecules through the total director vector extracted through the step (g), and then obtains their average square displacement, Rotational viscosity using the method to find the slope of the mean square displacement over time

Obtaining a; Including;
The (h) step,
After the analysis unit 300 obtains the mean square displacement by obtaining the square displacement of the average director of the mixed liquid crystal consisting of different liquid crystal molecules, using the method of calculating the rotational viscosity using Equation 2 Molecular dynamics computer simulation method for calculating the rotational viscosity of different liquid crystal mixtures.
&Quot; (2) "

; Gradient of Mean Square Displacement with Time of the Director of Liquid Crystal Molecular System Obtained by Molecular Dynamics Simulation
V; Average volume obtained through molecular dynamics simulation
T; Average temperature obtained through molecular dynamics simulation

; Boltzmann constant
The method of claim 4, wherein
The step (c)
Molecular dynamics computer simulation method for calculating the rotational viscosity of different liquid crystal mixture, characterized in that the preparation unit 100 using the force field of the Generalized AMBER Force Field (GAFF).
delete

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