CN114323950A - Molecular dynamics model verification method based on mechanical test result - Google Patents
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Abstract
The invention discloses a molecular dynamics model verification method based on a mechanical test result, which comprises the following steps: establishing a molecular dynamics simulation model based on a mechanical test; setting simulation parameters of the molecular dynamics simulation model; calculating and outputting a simulation result by adopting a molecular dynamics simulation method according to the simulation parameters; processing the data of the simulation result to obtain a simulation result; and step five, comparing and verifying the simulation result of the molecular dynamics with the mechanical test result. It has the following advantages: the verification method based on the mechanical test can fully reflect the physical properties of the material, is beneficial to verifying the simulation accuracy of the molecular dynamics, and has important significance for improving the reliability of the simulation result of the molecular dynamics and the wide application of the molecular dynamics technology.
Description
Technical Field
The invention relates to the technical field of molecular simulation methods, in particular to a molecular dynamics model verification method based on a mechanical test result.
Background
The molecular dynamics is a molecular simulation method, which mainly depends on Newton mechanics to simulate the motion of a molecular system, so as to extract samples from a system consisting of different states of the molecular system, thereby calculating the configuration integral of the system, and further calculating the thermodynamic quantity and other macroscopic properties of the system based on the result of the configuration integral. Compared with the Monte Carlo method, the method has higher accuracy and effectiveness on macroscopic property calculation, and can be widely applied to various fields of physics, chemistry, biology, materials, medicine and the like. The molecular dynamics simulation technology has the observation capability of atomic scale under the nanometer scale, becomes an important method for solving the problems of deformation and the like of materials under the nanometer scale, and has the advantages of good repeatability and research cost saving.
However, the accuracy of the molecular dynamics simulation is highly dependent on the accuracy of the molecular dynamics model, and researchers perform a lot of scientific researches through the molecular dynamics simulation technology, but the reliability of the simulation result is a question worth discussing, so that a verification method for checking the accuracy of the molecular dynamics model is required in the existing market to improve the reliability of the simulation result.
Disclosure of Invention
The invention provides a molecular dynamics model verification method based on a mechanical test result, which overcomes the defects in the background technology.
The technical scheme adopted by the invention for solving the technical problem is as follows: the molecular dynamics model verification method based on the mechanical test result comprises the following steps:
establishing a molecular dynamics simulation model based on a mechanical test;
setting simulation parameters of the molecular dynamics simulation model;
calculating and outputting a simulation result by adopting a molecular dynamics simulation method according to the simulation parameters;
processing the data of the simulation result to obtain a simulation result;
and step five, comparing and verifying the simulation result of the molecular dynamics with the mechanical test result.
In one embodiment: in the first step, LAMMPS software is adopted to establish a molecular dynamics simulation model based on a mechanical test.
In one embodiment: in the first step, a nano indentation mechanical test method is adopted to establish a combined model of a spherical pressure head and a massive matrix, wherein the pressure head and the matrix are both made of single crystal alumina, and the lattice parameters of the single crystal alumina are as follows:
the method comprises the following steps of (1) establishing a rigid spherical pressure head and a cuboid matrix through LAMMPS software, wherein alpha is 90 degrees and gamma is 120 degrees, and the matrix material is divided into three layers which are respectively a Newton layer, a constant temperature layer and a boundary layer; wherein Newton layer atoms follow Newton's second law, analog evolution is carried out under the action of potential function, the temperature of atoms in the constant temperature layer is controlled at 297K, and atoms in the boundary layer are fixed.
In one embodiment: in the second step, the simulation parameters comprise simulation dimensions, boundary conditions, potential functions, ensemble selection, system temperature control modes, simulation temperature and time steps.
In one embodiment: and step two, determining simulation parameters necessary for molecular dynamics simulation in LAMMPS software, wherein the simulation parameters comprise that the simulation dimension is three-dimensional, the initial temperature is 297K, the actual room temperature is simulated, the boundary condition is that the pressure head is a free boundary condition in the loading direction, the boundary condition is a periodic boundary condition in other directions, the time step is 1 femtosecond, the interatomic interaction potential adopts a potential function, the ensemble adopts isothermal and isobaric pressure in the balance stage, a micro-regular ensemble is adopted in the working stage of the pressure head, the type of an external load is a press-in load, the system temperature control mode is a speed calibration method, the loading and unloading rates are both 100m/s, and the loading depth is 7 nm.
In one embodiment: in the third step, the data of the simulation result includes the three-dimensional coordinates, the speed and the load of each atom in the simulation system.
In one embodiment: in the fourth step, the data processing of the simulation result comprises:
and (3) calculating to obtain the hardness, wherein the calculation formula is as follows: hardness of
Wherein P ismaxThe maximum load of the nano indentation is shown, A is the contact area under the maximum load, and the calculation formula of the contact area is that A is pi (2 Rh-h)2) Wherein R is the radius of the pressure head, and h is the loading depth;
and acquiring the surface morphology of the simulated indentation, and performing coloring marking by adopting OVITO software according to the coordinate of the atom in the Z direction to perform visual presentation.
In one embodiment: and fifthly, comparing and verifying the hardness and the indentation surface appearance of the molecular dynamics simulation result and the hardness and the indentation surface appearance of the mechanical test result.
In one embodiment: and step five, comparing and verifying the simulation result of the molecular dynamics with the mechanical test result, if the simulation result is not matched with the mechanical test result, modifying the simulation parameters and executing the step three until the simulation result is matched with the mechanical test result.
Compared with the background technology, the technical scheme has the following advantages:
the verification method based on the mechanical test can fully reflect the physical properties of the material, is beneficial to verifying the simulation accuracy of the molecular dynamics, has important significance for improving the reliability of the molecular dynamics simulation result and the wide application of the molecular dynamics technology, improves the calculation precision of the molecular dynamics simulation, and improves the reliability of the simulation result.
Drawings
The invention is further described with reference to the following figures and detailed description.
Fig. 1 is a flowchart of a molecular dynamics model verification method according to this embodiment.
Fig. 2 is a molecular dynamics simulation model based on nanoindentation in this embodiment.
Fig. 3 is a graph of the hardness of the nanoindentation of this embodiment as a function of loading depth.
FIG. 4 is a comparison graph of the simulated and tested indentation surface topography of this embodiment.
Detailed Description
The molecular dynamics model verification method based on the mechanical test result comprises the following steps:
firstly, adopting LAMMPS software to establish a molecular dynamics simulation model based on a mechanical test;
setting simulation parameters of the molecular dynamics simulation model, wherein the simulation parameters comprise simulation dimensions, boundary conditions, potential functions, ensemble selection, a system temperature control mode, simulation temperature and time steps;
calculating and outputting a simulation result by adopting a molecular dynamics simulation method according to the simulation parameters, wherein the data of the simulation result comprises the three-dimensional coordinate, the speed and the load of each atom in the simulation system;
processing the data of the simulation result to obtain a simulation result;
and step five, comparing and verifying the simulation result of the molecular dynamics with the mechanical test result, if the simulation result is not matched with the mechanical test result, modifying the simulation parameters and executing the step three until the simulation result is matched with the mechanical test result.
In the fourth step, the data processing of the simulation result comprises: and (3) calculating to obtain the hardness, wherein the calculation formula is as follows: hardness of
Wherein P ismaxThe maximum load of the nano indentation is shown, A is the contact area under the maximum load, and the calculation formula of the contact area is that A is pi (2 Rh-h)2) Wherein R is the radius of the pressure head, and h is the loading depth; and acquiring the surface morphology of the simulated indentation, and performing coloring marking by adopting OVITO software according to the coordinate of the atom in the Z direction to perform visual presentation.
And fifthly, comparing and verifying the hardness and the indentation surface appearance of the molecular dynamics simulation result and the hardness and the indentation surface appearance of the mechanical test result.
An application example of the molecular dynamics model verification method is described in detail below, and referring to fig. 1, the application example includes:
firstly, adopting LAMMPS software to establish a molecular dynamics simulation model:
a nano indentation mechanical test method is adopted to establish a combined model of a spherical pressure head and a blocky substrate, the pressure head and the substrate are both made of ideal single crystal alumina, and the lattice parameters of the single crystal alumina are as follows:
α ═ β ═ 90 ° and γ ═ 120 °, rigid spherical indents with a radius of 7nm and three-dimensional dimensions 28 × 28 × 23nm were built up by the LAMMPS software3The cuboid substrate is divided into three layers according to actual test working conditions, and the three layers are respectively a Newton layer, a constant temperature layer and a boundary layer. Wherein Newton layer atoms follow Newton's second law, and simulated evolution is carried out under the effect of potential function, and the constant temperature layer atom temperature is controlled at 297K, and the environmental temperature of simulation test, boundary layer atoms are fixed, prevent that the base body from translating in the loading process. Fig. 2 is an established model, in the present application example, the simulation mode adopts nano indentation, and according to actual needs, mechanical test methods such as nano scratch, uniaxial tension, compression, shearing and the like can also be adopted. In the application example, the substrate is in a cuboid shape, substrates in other shapes can be modeled according to needs, and the pressure head can also be in other shapes such as a triangular pyramid shape, a quadrangular pyramid shape and the like.
Secondly, setting simulation parameters of the molecular dynamics simulation model:
determining necessary simulation parameters for molecular dynamics simulation in LAMMPS software, wherein the simulation parameters comprise that the simulation dimension is three-dimensional, the initial temperature is 297K, the actual room temperature is simulated, the boundary condition is that the pressure head is in a free boundary condition in the loading direction, the boundary condition is in a periodic boundary condition in other directions, the time step is 1 femtosecond, the interatomic interaction potential adopts a Buckingham potential function, the system adopts NVT in the balance stage, NVE in the working stage of the pressure head, the type of an external load is an indentation load, the system temperature control mode is a speed calibration method, the loading and unloading rates are both 100m/s, and the loading depth is 7 nm.
Thirdly, performing molecular dynamics simulation calculation and outputting a simulation result, wherein the data of the simulation result comprises: the atom type, the charge quantity, the three-dimensional coordinate and the speed of the atom and the load on the pressure head atom corresponding to the atom number.
And fourthly, processing the output data of the molecular dynamics simulation to obtain a simulation result. And processing the material force and displacement data output by the lamemps, wherein OVITO software is adopted in the application example to perform visualization processing on the simulation data. Fig. 3 is a load displacement curve of the nanoindentation process, and fig. 4 is a change curve of hardness with the loading depth during the loading process.
Wherein the hardness calculation formula is as follows: hardness of
Wherein P ismaxThe maximum load of the nano indentation is shown, A is the contact area under the maximum load, and the calculation formula of the contact area is that A is pi (2 Rh-h)2) Wherein R is the radius of the pressure head, and h is the loading depth;
the acquisition of the simulated indentation morphology is performed by adopting OVITO software to perform coloring marking according to the coordinate of the atom in the Z direction for visual presentation.
And fifthly, comparing the simulation result of the molecular dynamics and the mechanical test result which comprise the hardness and the indentation surface appearance, and verifying the hardness and the indentation surface appearance of the simulation result of the molecular dynamics and the hardness and the indentation surface appearance of the mechanical test result to verify the reliability of the molecular dynamics simulation model.
And comparing the hardness of the single crystal alumina obtained in the test with the hardness value obtained in the simulation. The hardness value in the application example is obtained through a nano indentation test, the hardness value is 35.83 +/-1.6 GPa, a curve of the hardness in simulation along with the variation of the indentation depth is shown in figure 3, the simulated hardness value in the loading stable region is calculated and obtained to be 35.35 +/-0.9 GPa according to data obtained through simulation, the simulated and tested values are very close to each other in the hardness value view, and the error is within 2%. From the angle of the surface topography of the indentation, as shown in fig. 4, the indentation topography after the visualization processing by using the OVITO software shows the characteristic of obvious triple symmetry, and the triple symmetry on the same surface of the indentation topography obtained through the test. The accuracy of the molecular dynamics model of the embodiment is verified through the similarity of the hardness and the surface topography of the indentation.
Therefore, a molecular dynamics simulation model with reliability is obtained.
The above description is only a preferred embodiment of the present invention, and therefore should not be taken as limiting the scope of the invention, which is defined by the appended claims and their equivalents.
Claims (9)
1. The molecular dynamics model verification method based on the mechanical test result is characterized by comprising the following steps: the method comprises the following steps:
establishing a molecular dynamics simulation model based on a mechanical test;
setting simulation parameters of the molecular dynamics simulation model;
calculating and outputting a simulation result by adopting a molecular dynamics simulation method according to the simulation parameters;
processing the data of the simulation result to obtain a simulation result;
and step five, comparing and verifying the simulation result of the molecular dynamics with the mechanical test result.
2. The molecular dynamics model verification method based on mechanical test results according to claim 1, characterized in that: in the first step, LAMMPS software is adopted to establish a molecular dynamics simulation model based on a mechanical test.
3. The molecular dynamics model verification method based on mechanical test results according to claim 2, characterized in that: in the first step, a nano indentation mechanical test method is adopted to establish a spherical pressure head and a massive matrixThe combined model, pressure head, base member are all made by single crystal alumina, the single crystal alumina lattice parameter is:
the method comprises the following steps of (1) establishing a rigid spherical pressure head and a cuboid matrix through LAMMPS software, wherein alpha is 90 degrees and gamma is 120 degrees, and the matrix material is divided into three layers which are respectively a Newton layer, a constant temperature layer and a boundary layer; wherein Newton layer atoms follow Newton's second law, analog evolution is carried out under the action of potential function, the temperature of atoms in the constant temperature layer is controlled at 297K, and atoms in the boundary layer are fixed.
4. The molecular dynamics model verification method based on mechanical test results according to claim 1, characterized in that: in the second step, the simulation parameters comprise simulation dimensions, boundary conditions, potential functions, ensemble selection, system temperature control modes, simulation temperature and time steps.
5. The method for verifying molecular dynamics model based on mechanical test results according to claim 3, wherein: and step two, determining simulation parameters necessary for molecular dynamics simulation in LAMMPS software, wherein the simulation parameters comprise that the simulation dimension is three-dimensional, the initial temperature is 297K, the actual room temperature is simulated, the boundary condition is that the pressure head is a free boundary condition in the loading direction, the boundary condition is a periodic boundary condition in other directions, the time step is 1 femtosecond, the interatomic interaction potential adopts a potential function, the ensemble adopts isothermal and isobaric pressure in the balance stage, a micro-regular ensemble is adopted in the working stage of the pressure head, the type of an external load is a press-in load, the system temperature control mode is a speed calibration method, the loading and unloading rates are both 100m/s, and the loading depth is 7 nm.
6. The molecular dynamics model verification method based on mechanical test results according to claim 1, characterized in that: in the third step, the data of the simulation result includes the three-dimensional coordinates, the speed and the load of each atom in the simulation system.
7. The molecular dynamics model verification method based on mechanical test results according to claim 1, characterized in that: in the fourth step, the data processing of the simulation result comprises:
and (3) calculating to obtain the hardness, wherein the calculation formula is as follows: hardness of
Wherein P ismaxThe maximum load of the nano indentation is shown, A is the contact area under the maximum load, and the calculation formula of the contact area is that A is pi (2 Rh-h)2) Wherein R is the radius of the pressure head, and h is the loading depth;
and acquiring the surface morphology of the simulated indentation, and performing coloring marking by adopting OVITO software according to the coordinate of the atom in the Z direction to perform visual presentation.
8. The molecular dynamics model verification method based on mechanical test results according to claim 1, characterized in that: and fifthly, comparing and verifying the hardness and the indentation surface appearance of the molecular dynamics simulation result and the hardness and the indentation surface appearance of the mechanical test result.
9. The molecular dynamics model verification method based on mechanical test results according to claim 1, characterized in that: and step five, comparing and verifying the simulation result of the molecular dynamics with the mechanical test result, if the simulation result is not matched with the mechanical test result, modifying the simulation parameters and executing the step three until the simulation result is matched with the mechanical test result.
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