Cooperative regulation and control method for shape memory alloy point defect and magnetic configuration

Abstract

The invention discloses a collaborative regulation and control method for shape memory alloy point defects and magnetic configuration, belongs to the technical field of new materials, and relates to a computational simulation method based on a density functional theory. The method comprises the following steps of: firstly, constructing a crystal structure of a shape memory alloy containing a point defect as an internal parent phase through Materials Studio software, and converting a file type of the crystal structure into a. Vasp format by virtue of vaspkit software in a Linux system; coordinately regulating and controlling the parent phase crystal model and the magnetic configuration, respectively quantifying the formation energy of the ferromagnetic structure and the formation energy of the ferromagnetic structure in constraint conditions, and predicting the physical characteristics of a final product through a tetragonal distortion method. According to the method, the alloy defect type can be precisely designed from the atomic scale, the optimal crystal configuration of the point defect is defined, the root cause of the influence of the point defect on the parent phase stability is clarified from the angle of the electronic state density, and then the purpose of precisely regulating and controlling the physical characteristics of the alloy is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of new materials, and relates to a method for coordinated regulation of point defects and magnetic configuration of shape memory alloys. Background Art

[0002] Shape memory alloys are a type of alloy material that can "remember" its initial shape when the temperature or other conditions change. Shape memory alloys have been used in the aerospace field for more than 50 years due to their significant strain output and driving force. In 1969, shape memory alloy pipe joints were successfully applied to the oil pipeline of the US F14 fighter. After that, the mechanisms and structures designed with shape memory alloys were gradually applied to various aspects of the aerospace field, such as space compression release mechanisms, geometric adjustment of aircraft engine intake ducts, variant aircraft and shock absorbers.

[0003] However, for alloy materials, intrinsic defects are inevitable, and alloy point defects have a significant impact on the physical properties of the alloy, such as crystal structure, phase stability, martensitic phase transformation and magnetic properties. Hu Qingmiao et al. studied TiNi by using the Exact Muffin-tin Orbitals (EMTO) method combined with coherent potential approximate calculation. 1-x Zr x The results show that Zr atoms prefer to occupy the position of Ti atoms, while Ti atoms move to the position of Ni atoms. Li et al. and Ghosh et al. studied the annealing temperature and time of CoMnSb and Ni 50 Mn 36.5 Sn 13.5 The magnetocaloric properties of the alloy were explored and it was found that the magnetocaloric properties of the alloy were significantly improved, which may be related to the internal defects of the alloy.

[0004] Most of the existing methods for improving the physical properties of alloy materials are achieved through element doping. However, for magnetic materials, only the relevant physical properties of the ferromagnetic configuration are calculated, while the ferrimagnetic configuration is ignored. Therefore, we propose a method for coordinated regulation of point defects and magnetic configuration of shape memory alloys. Through the coordinated regulation of multiple point defects and magnetic configurations inside the alloy, the calculation accuracy can be guaranteed while obtaining good material properties without the need for doping with other elements. This has theoretical guiding significance for the development and application of shape memory alloys in the performance of aviation fields such as deformable aircraft, pipe joints and shock absorbers. Summary of the invention

[0005] The purpose of the present invention is to provide a method for coordinated regulation of point defects and magnetic configuration of shape memory alloys in view of the problems existing in the prior art, to calculate the formation energy and tetragonal distortion curve of defect crystals under different magnetic configurations using first principles, and to analyze the magnetic moment information and martensitic phase transition path of the system based on electronic structure information. The method of the present invention can narrow the gap between calculation and experimental results, ensure calculation accuracy, and improve the comprehensive performance of shape memory alloys, which is of certain significance.

[0006] In order to achieve the purpose of the above invention, the technical solution adopted by the present invention is: a method for coordinated regulation of point defects and magnetic configuration of shape memory alloys, comprising the following steps:

[0007] Step 1: Use Materials Studio software to construct the austenite unit cell of shape memory alloy, introduce point defects on this basis, and construct the input file POSCAR for VASP calculation.

[0008] Step 2: During the calculation process, the ferromagnetic and ferrimagnetic states of each defect condition of the alloy are calculated, the ground state energy and formation energy of the alloy structure are quantified within the constraints, and the magnetic configuration of the austenite parent phase of the alloy is determined.

[0009] Among them, the constraints are the interatomic forces and external pressures during the structural relaxation process, and the types of point defects, including vacancies, antisites and substitutions; the formation energy is obtained by substituting the total ground state energy of the system and the ground state energy of each atom into the formation energy formula, and the ground state energy is the energy of structural relaxation under the constraints.

[0010] Step 3, repeat the above steps, change the variables within the constraints, coordinately regulate point defects and magnetic configuration, analyze the formation energy and magnetic properties under different defects, and play a role in regulating the physical properties of shape memory alloys.

[0011] Step 4: Calculate the tetragonal distortion and electronic state density of the alloy austenite parent phase, predict the influence of point defects on the martensitic phase transformation and magnetic properties of the alloy, and reveal the fundamental reasons for the changes in phase stability and magnetic properties from the perspective of electronic state density.

[0012] The tetragonal distortion is to apply a certain specific stress to the austenite structure after structural relaxation, so that it changes from a highly ordered cubic structure to a tetragonal structure. The volume of the cubic structure is set to V, the lattice constant is a0, the lattice constants of the tetragonal structure are a and c, and the relationship between a and c is c = (1 + δ) a. In the calculation process of tetragonal distortion, according to the principle of constant unit cell volume, the austenite structure is subjected to lattice distortion with different tetragonal distortion rates c / a, and its atomic positions are optimized. The total ground state energy of the alloy system is calculated, and then the tetragonal distortion curve is drawn.

[0013] Preferably, the .CIF format file is exported by Materials Studio software, and converted into the .vasp format by means of vaspkit software under Linux system.

[0014] Preferably, the shape memory alloy is selected from X m Y n Z p alloy system.

[0015] Preferably, the formula for calculating the quantized formation energy is as follows:

[0016]

[0017] Among them, E f Indicates the formation energy of the alloy system (eV / atom); E total represents the total energy of the ground state (eV); E X 、E Y 、E Z They represent the total ground state energy of pure elements X, Y, and Z respectively, and m, n, and p represent the number of atoms of pure elements X, Y, and Z respectively.

[0018] Preferably, a vacancy point defect refers to a vacancy left behind when an atom in a unit cell leaves a sublattice point; an anti-site defect refers to a defect caused by one atom in a unit cell occupying a sublattice point of another atom; and a substitution point defect refers to a defect caused by the interchange of sublattice points of atoms of different types in a unit cell.

[0019] Preferably, the magnetic state of the austenite phase is divided into a ferromagnetic state and a ferrimagnetic state. The ferromagnetic state means that the spin magnetization directions of the magnetic atoms are all in the same direction; the ferrimagnetic state means that the spin magnetization directions of the normal atoms and the excess atoms in the magnetic atoms are opposite.

[0020] Preferably, the normal atoms refer to atoms located at the initial sublattice points of the stoichiometric alloy unit cell; the excess atoms refer to atoms not located at the initial sublattice points of the stoichiometric alloy unit cell.

[0021] Preferably, the calculation of the ground state energy of the unit cell system is based on the plane wave pseudopotential method VASP simulation software package under the framework of density functional theory, wherein the generalized gradient approximation GGA method under the projected augmented wave PAW is used to describe the exchange correlation function during the calculation process, and The improved tetrahedral point-integration method is used to implement the K-point grid setting. The cutoff energy in the structural relaxation is set to 1.3 times the maximum cutoff energy of the pure element in the system. The convergence criteria for total energy and interatomic forces are set to 1 meV and The two together constitute the basis for judging whether structural relaxation is completed.

[0022] Preferably, the K-point grid setting needs to be tested for convergence, and different K-point grid settings are performed on the same system. The optimal K-point grid is determined by balancing time and accuracy factors through the calculation formula of the formation energy.

[0023] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0024] 1. The method of the present invention can overcome the traditional "cooking-style" experimental method, save resources and time, and coordinately regulate the point defects and magnetic configuration of shape memory alloys based on first-principles calculations to achieve the purpose of efficiently screening alloy components.

[0025] 2. The method of the present invention can obtain the formation energy parameters of the shape memory alloy by only providing the position information of each atom in the alloy system. It is simple to operate, low in cost, easy to implement, and suitable for popularization and application.

[0026] 3. The method of the present invention only requires the unit cell information of the parent phase of the alloy system. The trend of the martensitic phase transformation path and the martensitic phase transformation temperature can be predicted through tetragonal distortion calculation. Samples that meet the requirements are selected for experimental verification, which can effectively save experimental costs.

[0027] 4. The method of the present invention can effectively make up for the shortcomings of insufficient understanding of the physical properties of materials during material application by calculating the electronic structure, and provide a better reference for improving alloy performance from the root. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the austenite phase crystal structure and magnetic configuration of the Ni8Mn6In2 alloy in the embodiment.

[0029] Figure 2 This is a convergence test of the K-point grid of the austenite phase of the Ni8Mn6In2 alloy in the embodiment.

[0030] Figure 3 The formation energy of austenite phase of Ni8Mn6In2 alloy under the coordinated regulation of point defects and magnetic configuration in the embodiment.

[0031] Figure 4 It is the total magnetic moment of the austenite phase of Ni8Mn6In2 alloy with different point defects under the most stable magnetic configuration in the embodiment.

[0032] Figure 5 It is the tetragonal distortion curve of Ni9Mn6In1 alloy when anti-site defect occurs under the most stable magnetic configuration in the embodiment.

[0033] Figure 6 It is the electronic state density of Ni9Mn6In1 alloy when anti-site defect occurs in the most stable magnetic configuration in the embodiment. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is described in detail below with reference to the accompanying drawings and specific examples, but the embodiments are not intended to limit the present invention.

[0035] The present invention proposes a method for coordinated regulation of point defects and magnetic configuration of shape memory alloys. The crystal structure of the parent phase of the shape memory alloy including point defects is constructed by Materials Studio software, and its file type is converted into .vasp format by means of vaspkit software under Linux system. The austenite parent phase crystal model and magnetic configuration are coordinated and regulated, the formation energy of ferromagnetic and ferrimagnetic austenite is quantified within the constraints, and the physical properties of the final product are predicted by the tetragonal distortion method. The present invention can accurately design the alloy defect type from the atomic scale, clarify the optimal crystal configuration of point defects, and clarify the fundamental reason for the influence of point defects on the parent phase stability from the perspective of electronic state density, thereby achieving the purpose of accurately regulating the physical properties of the alloy.

[0036] Embodiment 1:

[0037] A method for coordinated regulation of point defects and magnetic configuration of shape memory alloys, see Figures 1 to 6 As shown, the following steps are included:

[0038] Step 1: Construction of a defect model of a shape memory alloy system with the molecular formula Ni8Mn6In2.

[0039] Since the stoichiometric Ni2MnIn alloy does not undergo martensitic transformation and thus does not have shape memory effect, the non-stoichiometric Ni8Mn6In2 alloy is selected as a specific embodiment. The point defect types of the austenite phase of the non-stoichiometric Ni8Mn6In2 alloy system are mainly divided into three categories: vacancy, anti-site and substitution, with a total of fourteen defect models. Vacancy point defects include: V-Ni, V-Mn1-1, V-Mn1-2, V-Mn2-1, V-Mn2-2, V-In; anti-site defects include: Ni9Mn6In1, Ni7Mn6In3, Ni6Mn6In4; substitution point defects include: Ni-Mn1, Ni-Mn2, Ni-In, Mn1-In, Mn2-In.

[0040] The austenite unit cell of the non-stoichiometric Ni8Mn6In2 alloy has two excess Mn atoms occupying the sublattice sites of two In atoms compared to the austenite unit cell of the Ni2MnIn alloy. In the process of setting the magnetic configuration, the calculation of the ferromagnetic state is to set the initial magnetic moment directions of all Mn atoms, Ni atoms and In atoms to the positive direction; the calculation of the ferrimagnetic state is to set the initial magnetic moment directions of the four normal Mn atoms, Ni atoms and In atoms to the positive direction, and the initial magnetic moment directions of the two excess Mn atoms to the negative direction; the initial magnetic moment sizes of each atom are set to 2μ according to experience. B , 5μ B , 1μ B Taking the austenite unit cell of Ni8Mn6In2 alloy as an example, the specific settings of the ferromagnetic state in the POSCAR file are: MAGMOM = 8*2 4*5 2*5 2*1; the specific settings of the ferrimagnetic state are: MAGMOM = 8*2 4*5 2*-52*1. The atomic diagram is shown in Figure 1 shown.

[0041] The crystal structure 3D visualization software Materials Studio was used to construct the austenite unit cell and vacancy, antisite, and substitution point defects of the Ni8Mn6In2 alloy. The vaspkit software based on the Linux system was used to convert the .cif file into a .vasp file to form the POSCAR input file required for VASP calculation. The initial INCAR, KPOINT, and POTCAR files were also generated using the vaspkit software.

[0042] Step 2: Calculate the ground state energy and formation energy of the ferromagnetic and ferrimagnetic states for each of the above point defects to determine the most stable magnetic configuration of the alloy austenite parent phase.

[0043] Some key parameters are as follows: In the calculation process, the interaction between ions and electrons is described by the PAW method, and the exchange correlation potential between electrons is treated by the PBE approximation method under GGA. The improved tetrahedral point-integration method is used to implement the K-point grid setting. The cutoff energy in the structural relaxation is set to 1.3 times the maximum cutoff energy of the pure element in the system, that is, ENMAX = 351eV. The convergence criteria for total energy and interatomic forces are set to 1meV and The two together constitute the basis for judging whether the structural relaxation is complete. And the system ground state energy and magnetic moment are read in the output file OSZICAR.

[0044] The convergence test of the K-point grid was carried out, and the K-point grids of 4×4×4, 6×6×6, 8×8×8, 10×10×10, 12×12×12, 14×14×14 and 16×16×16 were selected to calculate the total energy of the ground state. The results are as follows Figure 2 As shown, the optimal K-point grid is determined to be 10×10×10 by balancing time and accuracy factors.

[0045] Modify the key parameters of the initial input files INCAR and KPOINTS generated in step 1.

[0046] The formation energy can be calculated according to the following formula:

[0047]

[0048] Among them, E f Indicates the formation energy of the alloy system (eV / atom); E total represents the total energy of the ground state (eV); E X 、E Y 、E Z They represent the total ground state energy of pure elements Ni, Mn, and In respectively, and m, n, and p represent the number of atoms of pure elements X, Y, and Z respectively.

[0049] To this end, the formation energy of austenite phase under various point defects in the alloy system is calculated, such as Figure 3 shown.

[0050] Step 3: Repeat the above steps, change the point defect type within the constraints, coordinately regulate the magnetic configuration, analyze the formation energy and magnetic properties under different defects, and play a role in regulating the physical properties of shape memory alloys.

[0051] The constraints mentioned are the interatomic forces and external pressure during structural relaxation, and the types of point defects, including vacancies, antisites, and substitutions.

[0052] Step 4, select the austenite phase with the most stable magnetic configuration under various point defects, calculate the tetragonal distortion and electronic state density of the alloy austenite phase, and predict the influence of point defects on the martensitic phase transformation and magnetic properties of the alloy.

[0053] The tetragonal distortion is to apply a certain specific stress to the austenite structure after structural relaxation, so that it changes from a highly ordered cubic structure to a tetragonal structure. The volume of the cubic structure is set to V, the lattice constant is a0, the lattice constants of the tetragonal structure are a and c, and the relationship between a and c is c = (1 + δ) a. In the calculation process of tetragonal distortion, according to the principle of constant unit cell volume, the austenite structure is subjected to lattice distortion with different tetragonal distortion rates c / a, and its atomic positions are optimized, and the total ground state energy of the alloy system is calculated, and then the tetragonal distortion curve is drawn.

[0054] For the Ni8Mn6In2 alloy system in this example, the most stable state of the alloy system's own point defects and magnetic configuration can be accurately analyzed by the coordinated regulation of vacancy, antisite and substitution point defects and magnetic configuration, and the root cause can be deeply analyzed from the perspective of electronic structure, thereby achieving the purpose of accurately regulating the physical properties of the alloy. The following is the analysis process:

[0055] Figure 1 Schematic diagram of the austenite phase crystal structure and magnetic configuration of Ni8Mn6In2 alloy.

[0056] from Figure 2 It can be seen that when the K point is greater than 6×6×6, the ground state energy of the alloy fluctuates within a certain range and reaches the minimum value at a K point grid of 16×16×16. The larger the K point, the higher the accuracy of the calculation, and the longer the calculation time under the same service configuration. From the calculation results, it can be seen that the ground state energy of the alloy at a K point grid of 10×10×10 is only 0.3meV different from that at a K point grid of 16×16×16. Therefore, in order to balance the relationship between calculation accuracy and time cost, austenite unit cells all use a K point grid of 10×10×10.

[0057] from Figure 3 It can be seen that for vacancy point defects, when there is a V-Ni defect, the formation energy of the ferromagnetic state and the ferrimagnetic state is very small, and the difference is only 0.39 meV / atom, indicating that the austenite phase presents a coexistence state of ferromagnetic and ferrimagnetic states. Therefore, it can be determined that vacancy defects will preferentially occupy the sublattice lattice of Ni with a smaller atomic radius, and the phase stability of austenite gradually decreases with the increase of the atomic radius of the replaced atom. For antisite defects, the formation energy of the austenite phase of the ferromagnetic Ni9Mn6In1 alloy is the lowest, which indicates that the austenite phase stability under antisite defects is E from high to low. f (Ni9Mn6In1)>E f (Ni7Mn6In3)>E f (Ni6Mn6In4). For substitutional point defects, Ni-Mn2 obtains the smallest formation energy among substitutional defect types in the ferromagnetic state (FM), indicating that the austenite phase formed after the Ni atoms and Mn2 atoms exchange positions is the most stable at high temperatures.

[0058] from Figure 4It can be seen that for vacancy point defects, the order of the total magnetic moment of the austenite phase from high to low is Mag(V-Mn)>Mag(V-Ni)>Mag(V-In). For anti-point defects, the ferromagnetism of the austenite phase from high to low is Mag(Ni9Mn6In1)>Mag(Ni7Mn6In3)>Mag(Ni6Mn6In4). For substitution point defects, the order of the ferromagnetism of the austenite phase from high to low is Mag(Mn1-In)=(Mn2-In)>Mag(Ni-Mn2)>Mag(Ni-In)>Mag(Ni-Mn1).

[0059] Taking the antisite defect as an example, the tetragonal distortion and electronic structure are calculated. The analysis results show that the Ni9Mn6In1 and Ni6Mn6In4 alloys undergo a magneto-structural coupling transition from the ferromagnetic austenite phase to the ferrimagnetic martensite phase; the Ni7Mn6In3 alloy does not undergo a significant martensitic magneto-structural coupling phase transition, but there may be a modulated martensitic transition. The tetragonal distortion curve of the Ni9Mn6In1 alloy is selected as a schematic diagram, as shown in Figure 5 shown.

[0060] from Figure 6 It can be seen that the spin-up and spin-down total state density curves of the austenite phase of the ferromagnetic Ni9Mn6In1 alloy are poorly symmetric, and the total state density near the Fermi level is at the peak position, indicating that the total magnetic moment of the alloy is large at this time and the austenite phase structure stability is poor.

[0061] Embodiment 2:

[0062] A method for coordinated regulation of point defects and magnetic configuration of shape memory alloys comprises the following steps:

[0063] Step 1: Use Materials Studio software to construct the austenite unit cell of the shape memory alloy, introduce point defects on this basis, and construct the input file POSCAR for VASP calculation;

[0064] Step 2, during the calculation process, the ferromagnetic and ferrimagnetic states of each defect of the alloy are calculated, the ground state energy and formation energy of the alloy structure are quantified within the constraints, and the magnetic configuration of the austenite parent phase of the alloy is determined;

[0065] The constraints are the interatomic forces and external pressures during the structural relaxation process, and the types of point defects, including vacancy point defects, anti-point defects, and substitution point defects; the formation energy is obtained by substituting the total ground state energy of the system and the ground state energy of each atom into the formation energy formula, and the ground state energy is the energy of structural relaxation under the constraints;

[0066] Step 3, repeat the above steps, change the variables within the constraints, coordinately regulate point defects and magnetic configuration, analyze the formation energy and magnetic properties under different defects, and play a role in regulating the physical properties of shape memory alloys;

[0067] Step 4: Calculate the tetragonal distortion and electronic state density of the alloy austenite parent phase, predict the influence of point defects on the martensitic phase transformation and magnetic properties of the alloy, and reveal the fundamental reasons for the changes in phase stability and magnetic properties from the perspective of electronic state density;

[0068] The tetragonal distortion is to apply a certain specific stress to the austenite structure after structural relaxation, so that it changes from a highly ordered cubic structure to a tetragonal structure; the volume of the cubic structure is set to V, the lattice constant is a0, the lattice constants of the tetragonal structure are a and c, and a and c show a relationship of c=(1+δ)a; in the calculation process of the tetragonal distortion, according to the principle of constant unit cell volume, the austenite structure is subjected to lattice distortion with different tetragonal distortion rates c / a, the atomic positions are optimized, the total ground state energy of the alloy system is calculated, and then the tetragonal distortion curve is drawn.

[0069] In the step 1, the .CIF format file is exported by Materials Studio software, and converted into .vasp format by means of vaspkit software under Linux system.

[0070] The shape memory alloy is selected from X m Y n Z p alloy system.

[0071] The formation energy formula is as follows:

[0072]

[0073] Among them, E f Indicates the formation energy of the alloy system (eV / atom); E total represents the total energy of the ground state (eV); E X 、E Y 、E Z They represent the total ground state energy of pure elements X, Y, and Z respectively, and m, n, and p represent the number of atoms of pure elements X, Y, and Z respectively.

[0074] The vacancy point defect refers to the vacancy left behind when an atom in a unit cell leaves a sublattice point; the anti-site defect refers to a defect caused by one atom in a unit cell occupying a sublattice point of another atom; and the substitution point defect refers to a defect caused by the interchange of sublattice points of atoms of different types in a unit cell.

[0075] The unit cells of all possible vacancies, anti-sites and substitution defects are constructed for the austenite parent phase, and the magnetic configuration of the austenite phase is set respectively, and the system formation energy is calculated by the formation energy formula.

[0076] The magnetic state of the austenite parent phase is divided into a ferromagnetic state and a ferrimagnetic state. The ferromagnetic state means that the spin magnetization directions of the magnetic atoms are all in the same direction; the ferrimagnetic state means that the spin magnetization directions of the normal atoms and the excess atoms in the magnetic atoms are opposite.

[0077] The normal atoms are atoms located at the initial sub-lattice points of the stoichiometric alloy unit cell; the excess atoms are atoms not located at the initial sub-lattice points of the stoichiometric alloy unit cell;

[0078] The calculation of the ground state energy is based on the VASP simulation software package of the plane wave pseudopotential method under the framework of density functional theory, wherein the interaction between ions and electrons is described by the PAW method during the calculation process, and the exchange correlation potential between electrons is processed by the PBE approximation method under GGA; The improved tetrahedral point-integration method realizes the K-point grid setting; the cutoff energy in the structural relaxation is set to 1.3 times the maximum cutoff energy of the pure element in the system; the convergence criteria of the total energy and interatomic force are set to 1 meV and The two together constitute the basis for judging whether structural relaxation is completed.

[0079] The K-point grid setting needs to be tested for convergence. Different K-point grid settings are performed on the same system. The optimal K-point grid is determined by balancing the time and accuracy factors through the calculation formula of the formation energy.

[0080] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, they are also intended to be included.

Claims

1. A method for coordinated regulation of point defects and magnetic configuration of shape memory alloys, characterized in that: The following steps are involved: Step 1: Use Materials Studio software to construct the austenite unit cell of the shape memory alloy, introduce point defects on this basis, and construct the input file POSCAR for VASP calculation; Step 2, during the calculation process, the ferromagnetic and ferrimagnetic states of each defect of the alloy are calculated, the ground state energy and formation energy of the alloy structure are quantified within the constraints, and the magnetic configuration of the austenite parent phase of the alloy is determined; The constraints are the interatomic forces and external pressures during the structural relaxation process, and the types of point defects, including vacancy point defects, anti-point defects, and substitution point defects; the formation energy is obtained by substituting the total ground state energy of the system and the ground state energy of each atom into the formation energy formula, and the ground state energy is the energy of structural relaxation under the constraints; Step 3, repeat the above steps, change the variables within the constraints, coordinately regulate point defects and magnetic configuration, analyze the formation energy and magnetic properties under different defects, and play a role in regulating the physical properties of shape memory alloys; Step 4: Calculate the tetragonal distortion and electronic state density of the alloy austenite parent phase, predict the influence of point defects on the martensitic phase transformation and magnetic properties of the alloy, and reveal the fundamental reasons for the changes in phase stability and magnetic properties from the perspective of electronic state density; The tetragonal distortion is to apply a certain specific stress to the austenite structure after structural relaxation, so that it changes from a highly ordered cubic structure to a tetragonal structure; the volume of the cubic structure is set to V, the lattice constant is a0, the lattice constants of the tetragonal structure are a and c, and a and c show a relationship of c=(1+δ)a; in the calculation process of the tetragonal distortion, according to the principle of constant unit cell volume, the austenite structure is subjected to lattice distortion with different tetragonal distortion rates c / a, the atomic positions are optimized, the total ground state energy of the alloy system is calculated, and then the tetragonal distortion curve is drawn.

2. The method for coordinated control of point defects and magnetic configuration of shape memory alloys according to claim 1, characterized in that: In the step 1, the .CIF format file is exported by Materials Studio software, and converted into .vasp format by means of vaspkit software under Linux system.

3. The method for coordinated control of point defects and magnetic configuration of shape memory alloys according to claim 1, characterized in that: The shape memory alloy is selected from X m Y n Z p alloy system.

4. The method for coordinated control of point defects and magnetic configuration of shape memory alloys according to claim 1, characterized in that: The formation energy formula is as follows: Among them, E f Indicates the formation energy of the alloy system (eV / atom); E total represents the total energy of the ground state (eV); E X 、E Y 、E Z They represent the total ground state energy of pure elements X, Y, and Z respectively, and m, n, and p represent the number of atoms of pure elements X, Y, and Z respectively.

5. The method for coordinated control of point defects and magnetic configuration of shape memory alloys according to claim 1, characterized in that: The vacancy point defect refers to the vacancy left behind when an atom in a unit cell leaves a sublattice point; the anti-site defect refers to a defect caused by one atom in a unit cell occupying a sublattice point of another atom; and the substitution point defect refers to a defect caused by the interchange of sublattice points of atoms of different types in a unit cell.

6. The method for coordinated control of point defects and magnetic configuration of shape memory alloys according to claim 4, characterized in that: The unit cells of all possible vacancies, anti-sites and substitution defects are constructed for the austenite parent phase, and the magnetic configuration of the austenite phase is set respectively, and the system formation energy is calculated by the formation energy formula.

7. The method for coordinated control of point defects and magnetic configuration of shape memory alloys according to claim 6, characterized in that: The magnetic state of the austenite parent phase is divided into a ferromagnetic state and a ferrimagnetic state. The ferromagnetic state means that the spin magnetization directions of the magnetic atoms are all in the same direction; the ferrimagnetic state means that the spin magnetization directions of the normal atoms and the excess atoms in the magnetic atoms are opposite.

8. The method for coordinated control of point defects and magnetic configuration of shape memory alloys according to claim 7, characterized in that: The normal atoms are atoms located at the initial sub-lattice points of the stoichiometric alloy unit cell; the excess atoms are atoms not located at the initial sub-lattice points of the stoichiometric alloy unit cell.

9. The method for coordinated control of point defects and magnetic configuration of shape memory alloys according to claim 1, characterized in that: The calculation of the ground state energy is based on the VASP simulation software package of the plane wave pseudopotential method under the framework of density functional theory, wherein the interaction between ions and electrons is described by the PAW method during the calculation process, and the exchange correlation potential between electrons is processed by the PBE approximation method under GGA; The improved tetrahedral point-integration method realizes the K-point grid setting; the cutoff energy in the structural relaxation is set to 1.3 times the maximum cutoff energy of the pure element in the system; the convergence criteria of the total energy and interatomic force are set to 1 meV and The two together constitute the basis for judging whether structural relaxation is completed.

10. The method for coordinated control of point defects and magnetic configuration of shape memory alloys according to claim 9, characterized in that: The K-point grid setting needs to be tested for convergence. Different K-point grid settings are performed on the same system. The optimal K-point grid is determined by balancing time and accuracy factors through the calculation formula of the formation energy.

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