SOC multilayer heterostructure stress characteristic and element diffusion evaluation method based on molecular dynamics

Abstract

The invention provides an SOC multilayer heterostructure stress characteristic and element diffusion evaluation method based on molecular dynamics, and the method comprises the following steps: S1, building a nanoparticle model of an LSFC-SDC electrode through employing Material Studio, and converting the nanoparticle model into a data file which can be recognized by molecular dynamics; s2, potential parameters of interaction force among all atoms in the LSFC-SDC electrode system are selected and fitted into a potential function, and the potential function is used for performing energy matching with a full-atom model; s3, simulating the sintering process of the LSFC-SDC electrode in Lammpps, including heating, heat preservation and cooling processes, setting boundary conditions, isothermal and isobaric ensemble conditions and sintering conditions at the same time, and collecting von Mises stress and mean square displacement of particles at each temperature node in the sintering process; s4, calculating a mean square displacement curve according to the mean square displacement, and obtaining a particle diffusion coefficient according to the mean square displacement curve; s5, calculating electrode stress and interface stress; according to the method, the particle diffusion behavior and the stress characteristic change rule of the LSFC-SDC electrode in the sintering process can be obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of electrodes, and more particularly, to a method for evaluating stress characteristics and element diffusion of a SOC multi-layer heterostructure based on molecular dynamics. Background Art

[0002] In solid oxide cells (SOCs), the phenomenon of B-site cation particle segregation in composite electrode materials is one of the key mechanisms leading to electrode performance degradation. In typical perovskite-type composite electrodes (such as La0.6Sr0.4Co0.2Fe0.8O3-δ, LSCF), B-site transition metal ions (Co, Fe, etc.) are prone to surface segregation to form Co-rich or Fe-rich secondary phases due to differences in element diffusion barriers and lattice stress accumulation during long-term high-temperature operation or cyclic conditions. This phase separation process significantly reduces the electrochemical activity of the electrode material: on the one hand, the loss of active sites directly weakens the catalytic activity of the oxygen reduction / evolution reaction (ORR / OER); on the other hand, the insulating phases (such as SrO, CoO, etc.) formed by segregation hinder the charge transport process, resulting in an increase in ohmic resistance. More seriously, during the cyclic switching process between fuel cell / electrolyzer modes, the dynamic segregation-dissolution behavior of B-site elements causes irreversible damage to the electrode microstructure, manifested as an abnormal increase in porosity and the fracture of the triple-phase boundary (TPB) network, ultimately leading to a decrease in the battery output power density by more than 35% and shortening the system life to 60%-70% of the design value. To alleviate this phenomenon, current research mostly uses element doping (such as introducing stable elements such as Zr and Nb at the B-site) or constructing a core-shell structure to inhibit element segregation.

[0003] To study the segregation phenomenon, experimental measurements are usually used to observe the atomic segregation phenomenon of LSFC-SDC electrode materials during the sintering process, including using X-ray diffraction and scanning electron microscopy to obtain images of atomic segregation in the material. However, the experimental preparation of materials is costly, time-consuming, and has many limitations. Therefore, it is necessary to use computer simulation to sinter the process. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for evaluating stress characteristics and element diffusion of a SOC multi-layer heterostructure based on molecular dynamics, which can obtain the particle diffusion behavior and stress characteristic change rules of LSFC-SDC electrodes during the sintering process.

[0005] The present invention provides a method for evaluating stress characteristics and element diffusion of a SOC multi-layer heterostructure based on molecular dynamics, including the following steps:

[0006] S1. Use Material Studio to build the nanoparticle model of the LSFC-SDC electrode and convert it into a data file that can be recognized by molecular dynamics;

[0007] S2, select the potential parameters of the interaction force between all atoms in the LSFC-SDC electrode system and fit them into a potential function for energy matching with the all-atom model;

[0008] S3. Simulate the sintering process of LSFC-SDC electrode in Lammps, including heating, insulation and cooling processes, set boundary conditions, isothermal and isobaric ensemble conditions and sintering conditions, and collect the von Mises stress and mean square displacement of particles at each temperature node during the sintering process.

[0009] S4, calculating a mean square displacement curve according to the mean square displacement, and obtaining a diffusion coefficient of the particles according to the mean square displacement curve;

[0010] S5. Calculate the electrode stress and interface stress of the LSFC-SDC electrode.

[0011] In a possible implementation, step S1 includes the following steps:

[0012] S11. Using Material Studio, the unit cell structure of LFO3 nanoparticles was established and doped. Sr was added to replace part of the La element at a doping ratio of 10%. Co was added to replace part of the Fe element at a doping ratio of 10%, thereby obtaining LFSC.

[0013] S12, after the cell structure of CeO2 is expanded, Sm element is added to replace part of Ce element, and the doping ratio is 10% to obtain SDC;

[0014] S13. Use the Build nanocluster method in Material Studio to build a LSFC nanocluster model with a particle size of 20 nm and a SDC nanocluster model with a particle size of 20 nm, and copy the cluster particles of the LSFC nanocluster model and the SDC nanocluster model, where the LSFC:SDC is 1:1, and place them in the simulation box. At the same time, assign the force field information of each atom in pcff, export the car and mdf files, and use the msi tool that comes with the molecular dynamics simulation software to convert them into data files that can be recognized by Lammps.

[0015] In a possible implementation, the potential function expression in step S2 is as follows:

[0016]

[0017] Among them, A represents the strength parameter related to the repulsive force within the van der Waals force framework, ρ ij represents the decay rate parameter related to the repulsive force within the van der Waals force framework, C ij represents the strength parameter related to the attractive force within the van der Waals force framework, r ij represents the distance between particles i and j, q i and q j represent ionic charges, ε represents the dielectric constant, and E mesh represents the electric potential contribution.

[0018] In a possible implementation, the sintering process in step S3 includes the following steps:

[0019] S31. Relax the La, Sr, Fe, Co, Sm, Ce, and O particles to reach the minimum energy state;

[0020] S32. Heat up and hold the equilibrium system at 1073K under the conditions of the isothermal and isobaric ensemble. Among them, in the first 200 ps, heat up from room temperature 300K to the target temperature 1073K, and then hold at 1073K for 300 ps to obtain the sintered structure;

[0021] S33. Keep the sintered structure in the NVT for a heating stage of 200 ps. The heating stage heats up from 300K to 1073K at 4K / ps, and then goes through a temperature holding stage of 300 ps. Finally, through cooling and re - equilibration, obtain the equilibrium structure at room temperature;

[0022] S34. Predict, calculate, and collect the thermal physical property parameters of the equilibrium structure, compile them in the in file, and then obtain the restart file for each stage through Lammps simulation. The step size is 1 fs, and the particle - particle - particle mesh solver is used to handle the long - range Coulomb interaction with a precision of 10 -5 .

[0023] In a possible implementation, the von Mises stress expression in step S3 is as follows:

[0024]

[0025] Among them, τ xy , τ yz and τ xz respectively represent the shear stresses in the three - dimensional directions along the y - axis, z - axis, and x - axis directions, and σ x , σ y and σ z respectively represent the normal stress components in the three - dimensional directions.

[0026] In a possible implementation, the mean - square displacement expression in step S3 is as follows:

[0027]

[0028] Among them, r(t) represents the distance of particle movement, and t0 represents the initial time.

[0029] In a possible implementation, the calculation of the diffusion coefficient in step S4 includes the following steps:

[0030] S42. Fit the mean square displacement data into a mean square displacement curve;

[0031] S43. Calculate the diffusion coefficient through the following formula:

[0032]

[0033] Among them, d represents the degree of freedom or dimension of the system, and t is the simulation time.

[0034] In a possible implementation, step S5 includes the following steps:

[0035] S51. Divide the interface region between LSFC and SDC according to the atomic type and spatial position, and set the thickness of the interface region to be 3 to 5 times the atomic layer spacing;

[0036] S52. Separate and label the atoms in the interface region through the group command in Lammps;

[0037] S53. Calculate the electrode stress and interface stress in the interface region through the following formula:

[0038]

[0039] Compared with the prior art, the present invention uses the molecular dynamics method to study the particle diffusion behavior and stress characteristic change law of LSFC-SDC materials during the sintering process, saving experimental costs and reducing difficulties. Evaluating the sintering process can better match the sintering experiment, ensuring the accuracy of predicting the diffusion coefficient and particle stress change of LSFC-SDC electrode materials, and at the same time saving a large amount of simulation resources. Brief Description of the Drawings

[0040] Figure 1 It is a schematic flow chart of the present invention;

[0041] Figure 2 It is a SEM schematic diagram of the sintering of LSFC-SDC and dense SSZ electrolyte;

[0042] Figure 3 It is a schematic diagram of the formation of LSFC;

[0043] Figure 4Schematic diagram of the formation of SDC;

[0044] Figure 5 Simulation diagram of the sintering process;

[0045] Figure 6 Schematic diagram of the diffusion coefficient and mean square displacement;

[0046] Figure 7 Von Mises stress distribution diagram;

[0047] Figure 8 Schematic diagram of the interface region. Specific implementation manners

[0048] First of all, those skilled in the art should understand that these implementation manners are only used to explain the technical principles of the embodiments of the present application, and are not intended to limit the protection scope of the embodiments of the present application. Those skilled in the art can make adjustments according to needs to adapt to specific application scenarios.

[0049] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0050] The embodiments of the present application disclose an evaluation method for the stress characteristics and element diffusion of the SOC multi-layer heterostructure based on molecular dynamics, including the following steps:

[0051] S1. Use Material Studio to establish a nanoparticle model of the LSFC-SDC electrode and convert it into a data file recognizable by molecular dynamics.

[0052] Step S1 includes the following steps:

[0053] S11. Establish the unit cell structure of the LFO3 nanoparticle through Material Studio and perform doping. By incorporating Sr element to replace part of the La element, the doping ratio is 10%, and by incorporating Co element to replace part of the Fe element, the doping ratio is 10%, to obtain LFSC;

[0054] S12. After expanding the unit cell structure of CeO2, incorporate Sm element to replace part of the Ce element, and the doping ratio is 10% to obtain SDC;

[0055] S13. Use the Build nanocluster method in Material Studio to build a 20nm LSFC nanocluster model and a 20nm SDC nanocluster model, and copy the cluster particles of the LSFC nanocluster model and the SDC nanocluster model, where LSFC:SDC is 1:1, and place them in the simulation box. At the same time, assign the force field information of each atom in pcff and export car and mdf files, and use the msi tool provided by the molecular dynamics simulation software to convert them into data files that can be recognized by Lammps. The upper part of the scanning electron microscope shows the RSOC porous electrode with LSFC-SDC material, and the lower part is the dense SSZ electrolyte layer. Figure 2 As shown, this embodiment selects the working part of the production line as the research area for modeling and simulation of the material sintering process.

[0056] Specifically, LSFC is La 0.9 Sr 0.1 Fe 0.9 Co 0.1 O 3-δ , SDC is Sm 0.2 Ce 0.8 O 1.9 , as attached Figure 3 As shown in the figure, after the cell structure of CeO2 is expanded, Sm is added to replace part of Ce element, and the doping ratio is 10%. 0.2 Ce 0.8 O 1.9 Before simulating the sintering process, the model needs to be verified. The thermophysical parameters, thermal expansion coefficient and thermal conductivity can be calculated to illustrate the rationality of the potential parameters for calculating the interaction between particles by combining the long-range Born potential function with the Buck potential function. The initial simulation box size is Attached Figure 3 (a) shows the LFO3 all-atom lattice structure, i.e., the LFO3 supercell structure. Figure 3 (b) is a coarse-grained lattice structure, i.e., La after LFO3 is doped with Sr and Co. 0.9 Sr 0.1 Fe 0.9 Co 0.1 O 3-δ The supercell structure, with a coarse-grained level of 3, consists of three atomic lattices along the X, Y, and Z directions. Figure 3 (c) is a single LSFC particle structure. Figure 3 Each coarse-grained particle in (b) represents an attached Figure 3 (a) The 27 atoms in the all-atom lattice. Figure 3(b) The large red coarse-grained particles in the center correspond to 27 oxygen atoms in the all-atom structure. Similarly, the large blue coarse-grained particles represent 27 nickel atoms in the all-atom structure. Coarse-grained modeling is used to be more appropriate for nanoparticles in the actual sintering process, and the development of the coarse-grained model is based on the all-atom model, considering mass, momentum, energy, and charge. Attached Figure 4 (a) is the CeO2 supercell structure, Attached Figure 4 (b) is the Sm-doped CeO2 Sm 0.2 Ce 0.8 O 2-δ supercell structure, Attached Figure 4 (c) is the structure of a single SDC particle.

[0057] S2. Select the potential parameters of the interaction forces between all atoms in the LSFC-SDC electrode system and fit them into a potential function for energy matching with the all-atom model.

[0058] The expression of the potential function in step S2 is as follows:

[0059] The decay rate parameter related to the repulsive force, C ij represents the strength parameter related to the attractive force within the framework of van der Waals forces, r ij represents the distance between particles i and j, q i and q j represent the ionic charges, ε represents the dielectric constant, and E mesh represents the potential contribution.

[0061] The Lennard-Jones potential function describes the interaction between atoms or molecules, especially when describing the van der Waals attractive and repulsive effects between non-polar atoms. For the sintering process of nanoparticles or nanocrystals, the LJ potential function can be used as a simple and effective model to simulate and describe the interaction between particles. The long-range interaction Coulomb potential calculated by the lattice includes long-range and short-range interactions. The short-range interaction has a cut-off value, and the long-range interaction outside the cut-off value is calculated using the lattice space. In the above expression of the potential function:

[0062]

[0063] where, W = W X , W Y , W z , and respectively represent the weights of the particles at r i at the grid point R, Φ(R) represents the electrostatic potential at R, and R c represents the cut-off point of the interaction, and ρ(R) represents the charge density at the grid point R, represents the gradient.

[0064]

[0065] Among them, h x , h y , h z are the grid point spacings in different dimensions, and the charge q(R) is obtained by distributing the particle charge to the grid points in two steps.

[0066]

[0067] Among them, W represents the weight of the particle at r i on the grid R.

[0068]

[0069] In this step, a smoothing function can also be used. In this embodiment, the Gaussian distribution function is used to further distribute the particle charge between the grid points to ensure the conservation of the total charge, improve the accuracy, reduce the error in the long-range interaction calculation, and improve the efficiency and applicability of the algorithm. The particle charge q(R) diffuses to the surrounding grid points to generate a smooth charge distribution q′(R), thereby improving the calculation accuracy. The specific expression is as follows:

[0070]

[0071] where f(r) represents the Gaussian distribution function or other linear distribution functions.

[0072] In this embodiment, the interatomic potential parameters of the MD model of LSFC-SDC are shown in the following table:

[0073]

[0074] In this embodiment, the LSFC-SDC electrode system contains a total of 1,181,400 atoms, namely La, Sr, Fe, Co, Sm, Ce, and O atoms.

[0075] S3. Simulate the sintering process of the LSFC-SDC electrode in Lammps, including the heating, holding, and cooling processes, and at the same time set the boundary conditions, isothermal-isobaric ensemble conditions, and sintering conditions, and collect the von Mises stress and mean square displacement of the particles at each temperature node during the sintering process.

[0076] The sintering process in step S3 includes the following steps:

[0077] S31. Relax the La, Sr, Fe, Co, Sm, Ce, and O particles to reach the minimum energy state;

[0078] S32. Heat up and hold the equilibrium system under the conditions of 1073K and isothermal isobaric ensemble. Among them, in the first 200ps, heat up from room temperature 300K to the target temperature 1073K, and then hold for 300ps at 1073K to obtain a sintered structure;

[0079] S33. Carry out a heating stage of 200ps for the sintered structure under NVT. In the heating stage, heat from 300K to 1073K at 4K / ps, and then go through a temperature holding stage of 300ps. Finally, obtain an equilibrium structure at room temperature through cooling and rebalancing;

[0080] S34. Predict, calculate and collect the thermal physical property parameters of the equilibrium structure, compile them in the in file, and then obtain the restart files of each stage through Lammps simulation. The time step is 1fs, and the particle-particle-particle mesh solver is used to handle the long-range Coulomb interaction with an accuracy of 10 -5 。

[0081] In step S3, the von Mises stress expression is as follows:

[0082]

[0083] Among them, τ xy , τ yz and τ xz respectively represent the shear stresses in the three-dimensional directions along the y-axis, z-axis, and x-axis, and σ x , σ y and σ z respectively represent the normal stress components in the three-dimensional directions.

[0084] In step S3, the mean square displacement expression is as follows:

[0085]

[0086] Among them, r(t) represents the distance of particle movement, and t0 represents the initial time.

[0087] S4. Calculate the mean square displacement curve based on the mean square displacement, and obtain the diffusion coefficient of the particles according to the mean square displacement curve.

[0088] The calculation of the diffusion coefficient in step S4 includes the following steps:

[0089] S42. Fit the mean square displacement data changes into a mean square displacement curve;

[0090] S43. Calculate the diffusion coefficient through the following formula:

[0091]

[0092] Among them, d represents the degrees of freedom or dimensions of the system, and t is the simulation time.

[0093] Specifically, as shown in the appendix Figure 5 As shown, the appendix Figure 5 (a) represents the initial stage, where the particles are randomly distributed in the cubic simulation box; appendix Figure 5 (b) At 500 ps, due to particle agglomeration, the simulation box shrank by 42.9%. In this embodiment, the line segment between the first 5 ps and 30 ps was selected to calculate the diffusion coefficient, which was calculated as a function of time based on the slope of the mean square displacement curve. To ensure the accuracy of the calculation, the linear region of the mean square displacement curve was selected, that is, the slope was fitted from 5 ps to 30 ps. Before heating, it was equilibrated at room temperature for 100 ps to ensure that the system reached a stable state before the sintering process. In the initial stage of sintering, as the temperature increased, the clusters began to aggregate. It was crucial to determine the main particles and elements causing this aggregation. Therefore, it was necessary to calculate the diffusion coefficient at this stage. The diffusion coefficient was very helpful for understanding the atomic interactions and atomic segregation. As shown in the appendix Figure 6 As shown, the appendix Figure 6 (a) represents the mean square displacement and diffusion coefficient of LSFC and SDC nanoparticles, appendix Figure 6 (b) represents the mean square displacement and diffusion coefficient of La, Sr, Fe, and Co particles during the sintering process.

[0094] S5. Calculate the electrode stress and interface stress of the LSFC-SDC electrode.

[0095] Step S5 includes the following steps:

[0096] S51. Divide the interface region between LSFC and SDC according to the atomic type and spatial position, and set the thickness of the interface region to 3 to 5 times the atomic layer spacing;

[0097] S52. Use the group command in Lammps to separately label the atoms in the interface region;

[0098] S53. Calculate the electrode stress and interface stress of the interface region through the following formula:

[0099]

[0100] Specifically, the interface region is as shown in the appendix Figure 8 As shown, in this embodiment, the atomic type is divided as follows: La, Sr, Fe, and Co belong to LSFC; Sm and Ce belong to SDC; Sc and Zr belong to SSZ. The thickness of the interface region is 1.5 nm to 2.5 nm, which is used to cover the interaction range of the three-phase atoms.

[0101] The method of calculating stress is compiled in the in file, and the von Mises stress of LSFC, SDC nanoparticles and atoms La, Sr, Fe and Co are calculated respectively. The data is obtained after sintering. The calculation principle of von Mises stress is as follows. Unlike macroscopic stress, the stress at the atomic / particle level depends partly on the mass and kinetic energy of the atomic particle. The other part depends on the potential energy of the interatomic forces and the positions of the atoms. p represents momentum, V voro is the effective volume, Represents the potential (tensor) between particles.

[0102]

[0103] The principle of von Mises stress is based on the concept of energy distortion, which holds that the elastic distortion stored when the material yields can reach a critical value, which is equivalent to the yield strength of the material. This equivalent uniaxial stress state can be used to predict whether the material will yield. If the von Mises stress reaches or exceeds the yield limit of the material, the material will undergo plastic deformation. In order to evaluate the stress distribution in the sintered structure, the von Mises stress yield criterion can be applied to determine the effective stress in the structure. Figure 7 As shown, attached Figure 7 (a) shows the nanoparticles of LSFC-SDC at the end of the sintering process. Figure 7 (b) shows LSFC and SDC nanoparticles, attached Figure 7 (c) represents the La, Sr, Fe and Co particles in the sintered particles. Figure 7 (a) is obtained using the open source software OVIT. After sintering, the obtained .xyz file is input into OVITO. In the Modifications column, select the Atomic strain option that has been written in the in file and output to the file in the simulation. After that, just adjust the upper and lower limits of the stress of the cloud map and optimize the color output.

[0104] It should be noted that a higher-level method, the "core-shell" model, can be used to distinguish the different diffusion behaviors and nuclear stress characteristics of atoms outside the shell and atoms inside the core. Machine learning methods can also be used to obtain more accurate force fields, improve the accuracy of calculations, and are not limited by the material system. Material Studio modeling software is converted into Lammps recognizable files. In addition to using the built-in msi. file conversion, you can also use ovito software and save the pdb format in the modeled periodic structure. Then, if it is a Windows system, open Powershell.

[0105] In the description of the embodiments of the present application, it should be noted that in the description of the present application, the terms "inner", "outer", etc., indicating the direction or positional relationship are based on the direction or positional relationship shown in the drawings. This is only for the convenience of description and does not indicate or imply that the device or component must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present application.

[0106] In the description of the present application, the descriptions referring to terms such as "one embodiment", "some embodiments", "in this embodiment", "specific examples", or "some examples", etc., mean that the specific features, mechanisms, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0107] The above is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An evaluation method for stress characteristics and element diffusion of SOC multi-layer heterostructures based on molecular dynamics, characterized in that, The following steps are involved: S1. Use Material Studio to build the nanoparticle model of the LSFC-SDC electrode and convert it into a data file that can be recognized by molecular dynamics; S2, selecting the potential parameters of the interaction force between all atoms in the LSFC-SDC electrode system and fitting them as a potential function for energy matching with the all-atom model; S3. Simulate the sintering process of the LSFC-SDC electrode in Lammps, including heating, heat preservation and cooling processes, set boundary conditions, isothermal and isobaric ensemble conditions and sintering conditions, and collect the von Mises stress and mean square displacement of the particles at each temperature node during the sintering process; S4, calculating a mean square displacement curve according to the mean square displacement, and obtaining a diffusion coefficient of the particles according to the mean square displacement curve; S5. Calculate the electrode stress and interface stress of the LSFC-SDC electrode.

2. The evaluation method of stress characteristics and element diffusion of the SOC multi-layer heterostructure based on molecular dynamics according to claim 1, wherein Step S1 includes the following steps: S11, establishing a unit cell structure of LFO3 nanoparticles through the Material Studio and performing doping, replacing part of the La element by doping Sr element at a doping ratio of 10%, and replacing part of the Fe element by doping Co element at a doping ratio of 10%, to obtain LFSC; S12, after the cell structure of CeO2 is expanded, Sm element is added to replace part of Ce element, and the doping ratio is 10% to obtain SDC; S13. Use the Build nanocluster method in the Material Studio to respectively build a LSFC nanocluster model with a particle size of 20 nm and a SDC nanocluster model with a particle size of 20 nm, and copy the cluster particles of the LSFC nanocluster model and the SDC nanocluster model, where the LSFC:SDC is 1:1, and place them in a simulation box. At the same time, allocate the force field information of each atom in pcff, export car and mdf files, and use the msi tool provided by the molecular dynamics simulation software to convert them into data files recognizable by Lammps.

3. The evaluation method of stress characteristics and element diffusion of the SOC multi-layer heterostructure based on molecular dynamics according to claim 2, wherein The potential function expression in step S2 is as follows: Among them, A represents the strength parameter related to the repulsive force within the van der Waals force framework, ρ ij represents the decay rate parameter related to the repulsive force within the van der Waals force framework, C ij represents the strength parameter related to the attractive force within the van der Waals force framework, r ij represents the distance between particles i and j, q i and q j represent the ionic charges, ε represents the dielectric constant, E mesh represents the electric potential contribution.

4. The evaluation method for stress characteristics and element diffusion of the SOC multi-layer heterostructure based on molecular dynamics according to claim 3, characterized in that The sintering process in step S3 includes the following steps: S31, relaxing La, Sr, Fe, Co, Sm, Ce and O particles to reach a minimum energy state; S32, heating and maintaining the equilibrium system at 1073K under isothermal and isobaric ensemble conditions, wherein the temperature is increased from room temperature 300K to a target temperature of 1073K for the first 200ps, and then maintained at 1073K for 300ps to obtain a sintered structure; S33, subjecting the sintered structure to a heating stage of 200 ps under NVT, wherein the heating stage is heated from 300 K to 1073 K at 4 K / ps, and then to a temperature holding stage of 300 ps, ​​and finally to cooling and rebalancing to obtain an equilibrium structure at room temperature; S34. Predict, calculate, and collect the thermal physical properties of the balance structure, compile them in the in file, and then obtain the restart files for each stage through Lammps simulation. The time step is 1 fs, and the particle-particle-particle mesh solver is used to handle the long-range Coulomb interaction with an accuracy of 10 -5 .

5. The evaluation method for stress characteristics and element diffusion of the SOC multi-layer heterostructure based on molecular dynamics according to claim 4, wherein The von Mises stress expression in step S3 is as follows: Among them, τ xy , τ yz and τ xz represent the shear stresses in the three-dimensional directions along the y-axis, z-axis, and x-axis respectively, and σ x , σ y and σ z represent the normal stress components in the three-dimensional directions respectively.

6. The evaluation method for stress characteristics and element diffusion of the SOC multi-layer heterostructure based on molecular dynamics according to claim 5, wherein The mean square displacement expression in step S3 is as follows: Among them, r(t) represents the distance the particle moves, and t0 represents the initial time.

7. The evaluation method for stress characteristics and element diffusion of the SOC multi-layer heterostructure based on molecular dynamics according to claim 6, characterized in that, The calculation of the diffusion coefficient described in step S4 includes the following steps: S42. Fit the change of the mean square displacement data into the mean square displacement curve; S43. Calculate the diffusion coefficient by the following formula: where d represents the degrees of freedom or dimension of the system, and t is the simulation time.

8. The evaluation method of stress characteristics and element diffusion of the SOC multi-layer heterostructure based on molecular dynamics according to claim 7, characterized in that, Step S5 includes the following steps: S51. Divide the interface region between LSFC and SDC according to the atomic type and spatial position, and set the thickness of the interface region to be 3 to 5 times the atomic layer spacing; S52. Use the group command in Lammps to separately label the atoms in the interface region; S53. Calculate the electrode stress and interface stress of the interface region by the following formula:

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