A molecular dynamics simulation method and medium for material grain boundaries

Abstract

The present invention relates to a molecular dynamics simulation method and medium for material grain boundaries, and to the technical field of material grain boundary simulation. Based on the principle of molecular dynamics, a crystal structure model of a preset material is constructed, and a coordinate system is established to obtain the charge amount, positive ion center, negative ion center and volume of each unit cell. For any coordinate direction, in response to the acquired charge amount, positive ion center, negative ion center and volume of each unit cell, the polarization value of each unit cell is calculated, and the average value of the polarization value is obtained; for any coordinate direction, the unit cell position where the grain boundary is located is judged based on the polarization value of each unit cell and the average value of the polarization value to obtain the unit cell position where the grain boundary is located; the unit cell position where the grain boundary is located in all coordinate directions is obtained. A method for determining the grain boundary of a material is provided from an experimental perspective, which provides a new research direction for grain boundary identification, so that the acquisition of the grain boundary can be simpler and more accurate.

Description

Technical Field

[0001] The invention relates to the technical field of material grain boundary simulation, and in particular to a molecular dynamics simulation method and medium for material grain boundaries. Background Art

[0002] In the analysis of materials, we often need to know the grain boundaries of the materials. Experimentally, it is difficult to accurately distinguish the grains and grain boundaries observed by SEM, TEM, and STEM images with the naked eye. With the continuous progress of computer science, machine learning methods are used to identify grain boundaries. The most important aspect of machine learning research is to develop the ability to quantitatively describe the atomic structure of GBs. In current research, atomic density, macroscopic and microscopic crystallographic parameters, and a large number of features based on neighbor bond lengths are used as descriptors of grain boundary structure. This method converts atomic position information into feature descriptions that can be used by machine learning models, which is a complex process, which may result in inaccurate identification of grain boundaries. Therefore, the current grain boundary identification still has the problem of low accuracy. In addition, machine learning methods require high computing power. Summary of the invention

[0003] The technical problem to be solved by the present application is to provide a molecular dynamics simulation method and medium for material grain boundaries, which has the characteristics of being able to more accurately determine material grain boundaries and provide a new research direction for grain boundary identification.

[0004] In a first aspect, an embodiment provides a molecular dynamics simulation method for a material grain boundary, comprising:

[0005] Construct the crystal structure model of the preset material based on the principle of molecular dynamics;

[0006] Identify each unit cell in the constructed crystal structure model, and establish a three-dimensional coordinate system with any unit cell as the coordinate origin;

[0007] Obtain the charge, positive ion center, negative ion center, and volume of each unit cell;

[0008] For any coordinate direction, in response to the acquired charge amount, positive ion center, negative ion center and volume of each unit cell in the any coordinate direction, the polarization value of each unit cell is calculated, and an average value of the polarization values ​​is obtained;

[0009] For any one of the coordinate directions, the unit cell position of the grain boundary is determined based on the polarization value of each unit cell and the average value of the polarization value, so as to obtain the unit cell position of the grain boundary;

[0010] Get the unit cell position of the grain boundary in all coordinate directions.

[0011] In one embodiment, for any coordinate direction, in response to the acquired charge amount, positive ion center, negative ion center and volume of each unit cell in the any coordinate direction, the polarization value of each unit cell is calculated, and the average value of the polarization value is obtained, including:

[0012] ;

[0013] ;

[0014] in, , , and Represents any coordinate direction m No. i The polarization value, volume, charge and distance between the positive and negative ion centers of each unit cell. The charge is the charge of the positive ion or the charge of the negative ion. The distance between the positive and negative ion centers is the distance between the positive ion center and the negative ion center. m Coordinate difference in direction; express m The average polarization value of each unit cell in the direction, n express m The number of unit cells in the direction, 1≤ i ≤ n。

[0015] In one embodiment, for any one of the coordinate directions, determining the unit cell position of the grain boundary based on the polarization value of each unit cell and the average value of the polarization value includes:

[0016] For the polarization value of any unit cell, the difference between the polarization value and the average value is calculated as the first difference;

[0017] It is determined whether the absolute value of the first difference is greater than a first difference threshold; if so, it is considered that the position of any unit cell is the position of the grain boundary.

[0018] In one embodiment, the method further includes: obtaining the width of the grain boundary in all coordinate directions; for the width of the grain boundary in any coordinate direction, the obtaining method includes:

[0019] The unit cell position of the obtained grain boundary is taken as the starting point, and the average polarization value is calculated layer by layer in the direction from the grain boundary to the inside of the grain in any coordinate direction, with the unit cell layer as the unit;

[0020] The unit cell layer whose variation trend of the average polarization value is greater than the set threshold is determined, and the width of the grain boundary is obtained based on the corresponding depth.

[0021] In one embodiment, the step of calculating the average polarization value layer by layer in units of unit cell layers includes:

[0022] Except for the last unit cell layer, the average polarization value corresponding to any unit cell layer is the average value of the polarization values ​​of the unit cells in that layer and all the unit cells from the grain boundary to the inside of the grain.

[0023] In one embodiment, the variation trend of the average polarization value is greater than the unit cell layer of the set threshold, and the width of the grain boundary is obtained based on the corresponding depth, including:

[0024] Determine whether the rate of change of the average polarization value corresponding to the first unit cell layer and the average polarization value corresponding to the second unit cell layer from the grain boundary to the interior of the grain is greater than the preset rate of change threshold; if so, determine whether the rate of change of the average polarization value corresponding to the second unit cell layer and the average polarization value corresponding to the third unit cell layer is greater than the preset rate of change threshold, until the rate of change of the average polarization value corresponding to the current unit cell layer and the average polarization value corresponding to the next unit cell layer is not greater than the preset rate of change threshold, then obtain the width of the grain boundary based on the thickness of all unit cell layers of the current layer and the previous layer.

[0025] In one embodiment, obtaining the width of the grain boundary based on the thickness of all unit cell layers of the current layer and the previous layer includes: taking twice the thickness of all unit cell layers of the current layer and the previous layer as the width of the grain boundary.

[0026] In one embodiment, if the rate of change of the average polarization value corresponding to the first unit cell layer and the average polarization value corresponding to the second unit cell layer is not greater than a preset rate of change threshold, a value not greater than twice the thickness of a single unit cell layer is taken as the width of the grain boundary.

[0027] In a second aspect, an embodiment provides a computer-readable storage medium, in which a program is stored, and the program can be loaded by a processor to execute the molecular dynamics simulation method of material grain boundaries described in any one of the above embodiments.

[0028] The beneficial effects of the present invention are:

[0029] Since a crystal structure model is first constructed based on the principle of molecular dynamics and a coordinate system is established, the charge of each unit cell, the positive ion center, the negative ion center and the volume of the unit cell can be known. In this way, the relationship between the polarization value of each unit cell in each direction and the average polarization value can be calculated. If the difference between the polarization value of the unit cell and the average value is obvious, it means that the position of the unit cell is the location of the grain boundary. This method provides a method for determining the grain boundaries of materials from an experimental perspective, provides a new research direction for grain boundary identification, and makes the acquisition of grain boundaries simpler and more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1This is a schematic diagram of a molecular dynamics simulation method for a material grain boundary according to an embodiment of the present application;

[0031] Figure 2 It is a polarization diagram of each BaTiO3 unit cell seen in a two-dimensional plane constructed by an embodiment of the present application;

[0032] Figure 3 This application Figure 1 A method flow diagram of an embodiment of step S50;

[0033] Figure 4 This is a schematic flow chart of a molecular dynamics simulation method for a material grain boundary according to another embodiment of the present application;

[0034] Figure 5 This is a schematic flow chart of a method for obtaining the width of a grain boundary in any coordinate direction according to an embodiment of the present application;

[0035] Figure 6 This is a schematic diagram of an average polarization value curve calculated layer by layer in units of unit cell layers in one embodiment of the present application;

[0036] Figure 7 It is identified in one embodiment of the present application Figure 2 Schematic diagram of the corresponding grain boundary. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below by specific embodiments in conjunction with the accompanying drawings. Wherein similar elements in different embodiments adopt associated similar element numbers. In the following embodiments, many detailed descriptions are for making the present application better understood. However, those skilled in the art can easily recognize that some features can be omitted in different situations, or can be replaced by other elements, materials, methods. In some cases, some operations related to the present application are not shown or described in the specification, this is to avoid the core part of the present application being overwhelmed by too much description, and for those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations according to the description in the specification and the general technical knowledge in the art.

[0038] In addition, the features, operations or characteristics described in the specification can be combined in any appropriate manner to form various implementations. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment and are not meant to be a required sequence, unless otherwise specified that a certain sequence must be followed.

[0039] The serial numbers assigned to the components in this article, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning.

[0040] To facilitate the description of the inventive concept of the present application, the material grain boundary identification technology is briefly described below.

[0041] In one current method, the orientation difference and inclination angle are discretized according to the orientation relationship between the two grains forming the grain boundary, and the distribution and relative energy of the grain boundary are expressed as a function of five degrees of freedom to identify different types of grain boundaries. In fact, the energy characteristics of different grain boundaries may be similar, which affects the accuracy of grain boundary identification.

[0042] In view of this, the present application provides a molecular dynamics simulation method and medium for material grain boundaries. In the method, a crystal structure model is first constructed based on the principle of molecular dynamics, and a coordinate system is established, so that the charge amount, positive ion center, negative ion center and volume of each unit cell can be known. In this way, the relationship between the polarization value of each unit cell in each direction and the average polarization value can be calculated. If the difference between the polarization value of the unit cell and the average value is obvious, it means that the position of the unit cell is the position of the grain boundary. This method provides a method for determining the grain boundary of a material from an experimental perspective, provides a new research direction for grain boundary identification, and makes the acquisition of grain boundaries simpler and more accurate.

[0043] In one embodiment of the present application, a molecular dynamics simulation method for a material grain boundary is provided. Please refer to Figure 1 ,include:

[0044] Step S10, constructing a crystal structure model of a preset material based on the principle of molecular dynamics.

[0045] Those skilled in the art will appreciate that the construction of the crystal structure model may be implemented based on existing technical software such as LAMMPS, GROMACS, Materials Studio, etc., which will not be described in detail here.

[0046] In one embodiment, the following description is made by taking the constructed barium titanate (BaTiO3) crystal structure model as an example.

[0047] Step S20, identifying each unit cell in the constructed crystal structure model, and establishing a three-dimensional coordinate system with any unit cell as the coordinate origin.

[0048] The established three-dimensional coordinate system includes an X-coordinate direction, a Y-coordinate direction, and a Z-coordinate direction.

[0049] Step S30, obtaining the charge amount, positive ion center, negative ion center and volume of each unit cell.

[0050] Based on the constructed barium titanate (BaTiO3) crystal structure model and the established coordinate system, we can know the charge of each BaTiO3 unit cell, the coordinate position of the positive ion center, the coordinate position of the negative ion center, and the volume of the BaTiO3 unit cell. Among them, the charge is the charge of the positive ion or the charge of the negative ion. Since the charge of the positive and negative ions is the same, whether the charge of the positive ion or the charge of the negative ion is used, the value of the charge is the same. For the BaTiO3 unit cell, the positive ion center refers to the center between the Ba ion and the Ti ion, and the negative ion center refers to the center between the three O ions.

[0051] Step S40, for any coordinate direction, in response to the acquired charge amount, positive ion center, negative ion center and volume of each unit cell in the any coordinate direction, calculate the polarization value of each unit cell and obtain the average value of the polarization value.

[0052] In one embodiment, step S40 may include:

[0053] ;

[0054] ;

[0055] in, , , and Represents any coordinate direction m No. i The polarization value, volume, charge and distance between the positive and negative ion centers of each unit cell. The charge is the charge of the positive ion or the charge of the negative ion. The distance between the positive and negative ion centers is the distance between the positive ion center and the negative ion center. m Coordinate difference in direction; express m The average polarization value of each unit cell in the direction, n express m The number of unit cells in the direction, 1≤ i ≤ n。

[0056] The m direction can be the X-axis direction, the Y-axis direction, or the Z-axis direction. Taking the X-axis direction as an example, if the coordinates of the center of the positive ion are (x1, y1, z1), and the coordinates of the center of the negative ion are (x2, y2, z2), then the distance between the centers of the positive and negative ions is x2-x1. Then the polarization value of each BaTiO3 unit cell in the X-axis direction can be calculated first, and then the average value of the polarization value of the BaTiO3 unit cell in the X-axis direction can be obtained. In this way, the polarization value of each BaTiO3 unit cell in each direction and the average value of the polarization value of the BaTiO3 unit cell can be obtained.

[0057] Please refer to Figure 2 , which is a polarization diagram of each BaTiO3 unit cell seen in a two-dimensional plane obtained in an embodiment of the present application, wherein each arrow represents the polarization value decomposed into each direction, wherein the length of the arrow represents the size of the polarization value, the red arrow represents the polarization value decomposed into the positive direction of the X-axis, the green arrow represents the polarization value decomposed into an angle close to 90 degrees with the X-axis direction, the blue arrow represents the polarization value decomposed into the negative direction of the X-axis, and the yellow arrow represents the polarization value decomposed into a direction between 90 degrees with the X-axis direction and the negative direction of the X-axis.

[0058] The applicant found in the study that the atoms in the material at the grain boundary are arranged irregularly, which leads to the displacement parameter, that is, the distance between the positive and negative ion centers. The difference between the internal and external grains is The difference of the parameter itself is still a small value and difficult to distinguish. In view of this, in one embodiment of the present application, the formula Will The polarization value obtained by multiplying the parameter by the charge and then dividing it by the overall volume of the unit cell is used to determine the mutation in the polarization size. The mutation point can be identified as a grain boundary.

[0059] Step S50 , for any coordinate direction, the unit cell position of the grain boundary is determined based on the polarization value of each unit cell and the average value of the polarization value, so as to obtain the unit cell position of the grain boundary.

[0060] In one embodiment, please refer to Figure 3 , step S50 may include:

[0061] Step S501: for a polarization value of any unit cell, calculate a difference between the polarization value and an average value as a first difference.

[0062] Taking the X-axis direction as an example, based on the average polarization value of the BaTiO3 unit cell in the X-axis direction, the first difference between the polarization value of each BaTiO3 unit cell in the X-axis direction and the average polarization value of the BaTiO3 unit cell in the X-axis direction can be calculated.

[0063] Step S502 , determining whether the absolute value of the first difference is greater than a first difference threshold, and if so, considering that the position of any unit cell is the position of the grain boundary.

[0064] Taking the X-axis direction as an example, if the absolute value of the first difference corresponding to a BaTiO3 unit cell is greater than the first difference threshold, it is considered that the BaTiO3 unit cell has a mutation, that is, the position of the BaTiO3 unit cell is the position of the grain boundary.

[0065] Step S60, obtaining the unit cell positions of the grain boundaries in all coordinate directions.

[0066] Based on step S50, the position of the grain boundary in each coordinate direction can be obtained.

[0067] In one embodiment, please refer to Figure 4 The molecular dynamics simulation method of the material grain boundary of the embodiment of the present application also includes:

[0068] Step S70, obtaining the width of the grain boundary in all coordinate directions, thereby obtaining accurate unit cell positions and widths, and obtaining more accurate molecular dynamics simulation results of the material grain boundary.

[0069] In one embodiment, please refer to Figure 5 , for the width of the grain boundary in any coordinate direction, the acquisition method includes:

[0070] Step S100 , taking the unit cell position of the obtained grain boundary as the starting point, and calculating the average polarization value layer by layer in the direction from the grain boundary to the inside of the grain in any coordinate direction, with the unit cell layer as the unit.

[0071] Please refer to Figure 6 , where Px represents the average polarization value curve in the X-axis direction, Py represents the average polarization value curve in the Y-axis direction, and Pz represents the average polarization value curve in the Z-axis direction. The abscissa represents the index of the unit cell layer from the grain boundary to the inside of the grain, and the ordinate represents the average planned value of the calculated grain polarization, in units of C / m 2 (Coulombs per square meter).

[0072] In one embodiment, the average polarization value is calculated layer by layer in units of unit cell layers, including: except for the last unit cell layer, the average polarization value corresponding to any unit cell layer is the average value of the polarization values ​​of the unit cell in any layer and all unit cells in the direction from the grain boundary to the inside of the grain.

[0073] exist Figure 6 In the example of the X-axis direction, the average polarization value corresponding to the first unit cell layer from the grain boundary to the interior of the grain is the average of the polarization values ​​of the first unit cell layer, the polarization value of the second unit cell layer, the polarization value of the third unit cell layer, the polarization value of the fourth unit cell layer, and the polarization value of the fifth unit cell layer. The average polarization value corresponding to the second unit cell layer is the average of the polarization value of the second unit cell layer, the polarization value of the third unit cell layer, the polarization value of the fourth unit cell layer, and the polarization value of the fifth unit cell layer. The average polarization value corresponding to the fifth unit cell layer is the polarization value of the fifth unit cell layer. In this way, the influence of the mutation in the previous unit cell layer on the calculation of the average polarization value of the subsequent unit cell layer is reduced.

[0074] Step S200 , determining the unit cell layer whose average polarization value variation trend is greater than a set threshold, and obtaining the width of the grain boundary based on the corresponding depth.

[0075] In one embodiment, step S200 includes: determining whether the rate of change of the average polarization value corresponding to the first layer of unit cell layers and the average polarization value corresponding to the second layer of unit cell layers from the grain boundary to the interior of the grain is greater than a preset rate of change threshold; if so, determining whether the rate of change of the average polarization value corresponding to the second layer of unit cell layers and the average polarization value corresponding to the third layer of unit cell layers is greater than a preset rate of change threshold; until the rate of change of the average polarization value corresponding to the current layer of unit cell layers and the average polarization value corresponding to the next layer of unit cell layers is not greater than the preset rate of change threshold, then the width of the grain boundary is obtained based on the thickness of all unit cell layers of the current layer and the previous layer.

[0076] In one embodiment, Figure 6 Taking the X-axis direction in the figure as an example, the change rate of the average polarization value Px1 corresponding to the first unit cell layer and the average polarization value Px2 corresponding to the second unit cell layer can be obtained. It can be expressed as: =(Px2-Px1) / Px1, we can get the change rate of the average polarization value Px2 corresponding to the second unit cell layer and the average polarization value Px3 corresponding to the third unit cell layer It can be expressed as: =(Px3-Px2) / Px2. In the embodiment of the present application, the obtained is greater than the preset change rate threshold, the obtained is less than a preset rate of change threshold, therefore, based on the depth corresponding to the second unit cell layer, that is, based on the thickness of the unit cell layers of the second layer and the first layer, the width of the grain boundary is obtained.

[0077] In one embodiment, the width of the grain boundary is obtained based on the thickness of all the unit cell layers of the current layer and the previous layer, including: taking twice the thickness of all the unit cell layers of the current layer and the previous layer as the width of the grain boundary. Figure 6 Taking the X-axis direction in the figure as an example, the thickness of the first unit cell layer plus the thickness of the second unit cell layer is twice the sum of the thickness as the width of the grain boundary. Taking the BaTiO3 unit cell as an example, the width of the grain boundary can be obtained to be 1.6nm.

[0078] If the rate of change of the average polarization value corresponding to the first layer of the unit cell layer and the average polarization value corresponding to the second layer of the unit cell layer is not greater than the preset rate of change threshold, it can be considered that the width of the grain boundary is small and the width of the grain boundary cannot be accurately identified. Therefore, in one embodiment, if the rate of change of the average polarization value corresponding to the first layer of the unit cell layer and the average polarization value corresponding to the second layer of the unit cell layer is not greater than the preset rate of change threshold, then the value not greater than twice the thickness of the single layer of the unit cell layer is taken as the width of the grain boundary. Taking the BaTiO3 unit cell as an example, the width of the grain boundary can be obtained to be ≤0.8nm. In one embodiment, a person skilled in the art can specify a value of ≤0.8nm as the width of the grain boundary based on experience.

[0079] In one embodiment, please refer to Figure 7 , which is identified based on the embodiment of the present application solution Figure 2 Schematic diagram of the corresponding two-dimensional plane of the grain boundary.

[0080] Based on the above scheme, the acquisition of grain boundaries can be simpler and more accurate, providing a new research direction for grain boundary identification.

[0081] In one embodiment of the present application, a computer-readable storage medium is provided, on which a program is stored. The stored program includes a method that can be loaded by a processor and process any of the above embodiments.

[0082] Those skilled in the art will appreciate that all or part of the functions of the various methods in the above-mentioned embodiments can be implemented by hardware or by computer programs. When all or part of the functions in the above-mentioned embodiments are implemented by computer programs, the program can be stored in a computer-readable storage medium, and the storage medium can include: read-only memory, random access memory, disk, optical disk, hard disk, etc., and the program is executed by a computer to implement the above-mentioned functions. For example, the program is stored in the memory of the device, and when the program in the memory is executed by the processor, all or part of the above-mentioned functions can be implemented. In addition, when all or part of the functions in the above-mentioned embodiments are implemented by computer programs, the program can also be stored in a storage medium such as a server, another computer, disk, optical disk, flash disk or mobile hard disk, and can be downloaded or copied and saved in the memory of the local device, or the system of the local device is updated, and when the program in the memory is executed by the processor, all or part of the functions in the above-mentioned embodiments can be implemented.

[0083] The above specific examples are used to illustrate the present invention, which is only used to help understand the present invention and is not intended to limit the present invention. For those skilled in the art, according to the concept of the present invention, some simple deductions, modifications or substitutions can be made.

Claims

1. A molecular dynamics simulation method for material grain boundaries, characterized in that: include: Construct the crystal structure model of the preset material based on the principle of molecular dynamics; Identify each unit cell in the constructed crystal structure model, and establish a three-dimensional coordinate system with any unit cell as the coordinate origin; Obtain the charge, positive ion center, negative ion center, and volume of each unit cell; For any coordinate direction, in response to the acquired charge amount, positive ion center, negative ion center and volume of each unit cell in the any coordinate direction, the polarization value of each unit cell is calculated, and an average value of the polarization values ​​is obtained; For any one of the coordinate directions, based on the polarization value of each unit cell and the average value of the polarization value, the unit cell position where the grain boundary is located is determined to obtain the unit cell position where the grain boundary is located, including: for the polarization value of any one of the unit cells, calculating the difference between the polarization value and the average value as a first difference; determining whether the absolute value of the first difference is greater than a first difference threshold, and if so, considering that the position where the any one of the unit cells is located is the position where the grain boundary is located; Get the unit cell position of the grain boundary in all coordinate directions.

2. The molecular dynamics simulation method of material grain boundaries according to claim 1, characterized in that: The method of calculating the polarization value of each unit cell in response to the acquired charge amount, positive ion center, negative ion center and unit cell volume of each unit cell in any coordinate direction and obtaining the average value of the polarization value includes: ， ， in, , , and Represents any coordinate direction m No. i The polarization value, volume, charge and distance between the positive and negative ion centers of each unit cell. The charge is the charge of the positive ion or the charge of the negative ion. The distance between the positive and negative ion centers is the distance between the positive ion center and the negative ion center. m Coordinate difference in direction; express m The average polarization value of each unit cell in the direction, n express m The number of unit cells in the direction, .

3. The molecular dynamics simulation method of material grain boundaries according to claim 1, characterized in that: Also includes: Get the width of the grain boundary in all coordinate directions; For the width of the grain boundary in any coordinate direction, the acquisition method includes: The unit cell position of the obtained grain boundary is taken as the starting point, and the average polarization value is calculated layer by layer in the direction from the grain boundary to the inside of the grain in any coordinate direction, with the unit cell layer as the unit; The unit cell layer whose variation trend of the average polarization value is greater than the set threshold is determined, and the width of the grain boundary is obtained based on the corresponding depth.

4. The molecular dynamics simulation method of material grain boundaries according to claim 3, characterized in that: The method of calculating the average polarization value layer by layer in units of unit cell layers includes: Except for the last unit cell layer, the average polarization value corresponding to any unit cell layer is the average value of the polarization values ​​of the unit cells in that layer and all the unit cells from the grain boundary to the inside of the grain.

5. The molecular dynamics simulation method of material grain boundaries according to claim 4, characterized in that: The variation trend of the average polarization value is greater than the unit cell layer of the set threshold, and the width of the grain boundary is obtained based on the corresponding depth, including: Determine whether the rate of change of the average polarization value corresponding to the first unit cell layer and the average polarization value corresponding to the second unit cell layer from the grain boundary to the interior of the grain is greater than the preset rate of change threshold; if so, determine whether the rate of change of the average polarization value corresponding to the second unit cell layer and the average polarization value corresponding to the third unit cell layer is greater than the preset rate of change threshold, until the rate of change of the average polarization value corresponding to the current unit cell layer and the average polarization value corresponding to the next unit cell layer is not greater than the preset rate of change threshold, then obtain the width of the grain boundary based on the thickness of all unit cell layers of the current layer and the previous layer.

6. The molecular dynamics simulation method of material grain boundaries according to claim 5, characterized in that: The obtaining of the width of the grain boundary based on the thickness of all the unit cell layers of the current layer and the previous layer includes: taking twice the thickness of all the unit cell layers of the current layer and the previous layer as the width of the grain boundary.

7. The molecular dynamics simulation method of material grain boundaries according to claim 5, characterized in that: If the change rate of the average polarization value corresponding to the first unit cell layer and the average polarization value corresponding to the second unit cell layer is not greater than a preset change rate threshold, a value not greater than twice the thickness of a single unit cell layer is taken as the width of the grain boundary.

8. A computer-readable storage medium, characterized in that: The medium stores a program, which can be loaded by a processor and execute the molecular dynamics simulation method of material grain boundaries as claimed in any one of claims 1 to 7.

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