A high-pressure metamagnetic material design method based on first-principle calculation

Abstract

The application provides a high-pressure phase intersecting metamagnetic material design method based on first principle calculation, and comprises the following steps: constructing a corresponding crystal model based on a plurality of phase structures of a candidate antiferromagnetic material; setting a plurality of potential antiferromagnetic configurations for each phase structure; determining a stable antiferromagnetic configuration under each phase structure; performing structure optimization on each phase to determine a zero-pressure phase and a high-pressure phase of the candidate material, and obtaining a pressure range in which each phase structure stably exists; and performing electronic property calculation, obtaining an electronic band structure of each phase structure of the candidate material through first principle calculation, and judging whether the high-pressure phase of the candidate material has metamagnetism by observing whether the band structure has an intersecting splitting phenomenon. The application uses an economical and accurate method to analyze whether the high-pressure phase of the material has metamagnetism, reduces the calculation cost, avoids a complicated and time-consuming experimental procedure, and thus speeds up the discovery of the metamagnetic material.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of magnetic material design, in particular to a high-pressure phase interchanging magnetic material design method based on first-principle calculation. BACKGROUND

[0002] Magnetic materials have important applications in modern information technology. Recent theoretical studies have shown that in some magnetic materials with zero net magnetic moment, even without spin-orbit coupling, the energy band structure will exhibit spin splitting, and this splitting occurs in an interlaced manner, thus giving rise to the new concept of "interchanging magnetism". Unlike the spin splitting caused by Rashba-Dresselhaus effect and Zeeman effect, this spin splitting has non-relativistic momentum-dependent characteristics. In fact, there is a unique spin group symmetry in interchanging magnetic materials, resulting in d-wave, g-wave and i-wave anisotropic spin splitting. The moment generated by this spin splitting is not constrained by the strength of the material's spin-orbit coupling, and it also allows for efficient manipulation of transverse spin current. In addition, the energy band of the spin splitting is the key to realizing the anomalous Hall effect, which produces a transverse voltage difference due to electron spin polarization without an external magnetic field. These characteristics indicate that interchanging magnetic materials have great application potential in the fields of spintronics and quantum computing. Therefore, further development of new interchanging magnetic materials has important technical value.

[0003] Traditional material development mainly uses the trial-and-error method, which has a great deal of randomness, resulting in a long development cycle. At the same time, when exploring the properties under extreme conditions such as high pressure, the development cost of the traditional trial-and-error method will increase dramatically. We know that first-principle calculation can completely calculate the performance of a material from the types and arrangement of its constituent atoms without any experimental data. It is worth mentioning that first-principle calculation can simulate extreme high-pressure environments that are difficult to achieve under external conditions by setting parameters. Therefore, using first-principle calculation to obtain the magnetic properties of high-pressure phases is a more practical research approach. This method not only greatly reduces the development cost, but also explores more abundant electronic structures, which helps to clarify whether the energy band has an interlaced characteristic and facilitates the discovery of more interchanging magnetic materials. SUMMARY

[0004] The purpose of the present application is to provide a high-pressure phase interchanging magnetic material design method based on first-principle calculation, which is used to study the electronic band structure of the high-pressure phase of a material, thereby discovering new interchanging magnetic materials and expanding the library of interchanging magnetic materials.

[0005] The technical scheme adopted by the present application is as follows: a high-pressure phase interchanging magnetic material design method based on first-principle calculation, which is applicable to antiferromagnetic materials with multiple crystal structures, comprising the following steps:

[0006] Step 1: Based on the multiple phase structures of the candidate antiferromagnetic material, construct the corresponding crystal model;

[0007] Step 2: For each phase structure, set multiple potential antiferromagnetic configurations;

[0008] Step 3: Determine the stable antiferromagnetic configuration under each phase structure by comparing the Gibbs free energy of each potential antiferromagnetic configuration;

[0009] Step 4: Optimize the structure of each phase, determine the zero-pressure phase and high-pressure phase structure of the candidate material according to the Gibbs free energy, and obtain the pressure range in which each phase structure is stable;

[0010] Step 5: Electronic property calculation, obtain the electronic band structure of each phase structure of the candidate material through first-principles calculation. By observing whether there is an interlaced splitting phenomenon in the band, it can be judged whether the high-pressure phase of the candidate material has alternating magnetism.

[0011] Further, in step 1, it can be specifically divided into the following steps:

[0012] Step 1-1: Through literature research or based on experimental results, obtain multiple phase structures of the candidate antiferromagnetic material;

[0013] Step 1-2: Use AMS software to construct the crystal model of each phase structure of the candidate material. The specific crystal structure information includes the type and number of atoms, the crystal system, the space group information, the bond length and bond angle between atoms, the cell angle, the number of atoms in the cell, the cell size, the cell volume, etc.

[0014] Further, in step 2, it can be specifically divided into the following steps:

[0015] Step 2-1: Set multiple potential antiferromagnetic configurations according to the crystal structure;

[0016] Step 2-2: Set the spin arrangement direction of the magnetic atoms according to the requirements.

[0017] In step 3, it can be specifically divided into the following steps:

[0018] Step 3-1: Use AMS-QE software to optimize the structure of each phase structure under multiple potential antiferromagnetic configurations;

[0019] Step 3-2: Set the parameters required for structure optimization, including the selection of high-symmetry wave vector (k) point grid, cutoff energy, strong Coulomb correlation U between atoms eff , frozen core, whether to fix the lattice, convergence energy, etc.

[0020] Step 3-3: Determine the stable antiferromagnetic configuration under each phase structure by comparing the Gibbs free energy of each potential antiferromagnetic configuration.

[0021] Furthermore, the step 4 can be specifically divided into the following steps:

[0022] Step 4-1: Use AMS-QE software to optimize the structure of each phase in the stable antiferromagnetic configuration, applying a certain range of pressure and gradually increasing pressure during the optimization;

[0023] Step 4-2: Set the parameters required for structure optimization, including the selection of high symmetry wave vector (k) point grid, cutoff energy, strong Coulomb correlation between atoms U eff , frozen core, converged energy, etc. When optimizing the structure, the lattice needs to be fixed to prevent the lattice from deforming under high pressure;

[0024] Step 4-3: By comparing the relationship between Gibbs free energy and pressure under each phase structure, determine the zero-pressure phase and high-pressure phase structures of the candidate material, and obtain the pressure range in which each phase structure exists stably.

[0025] Furthermore, the step 5 can be specifically divided into the following steps:

[0026] Step 5-1: Use AMS-BAND software to calculate the electronic band structure of each phase structure of the candidate material through first-principles calculations;

[0027] Step 5-2: Set the electronic properties calculation parameters according to specific needs, including the choice of calculation method, the strong Coulomb correlation effect U between atoms eff , frozen core, convergence energy, whether to consider the spin polarization behavior of electrons, parameterization and basis set selection, whether to consider spin-orbit coupling (SOC), etc. Other parameters can be set according to needs;

[0028] Step 5-3: By observing whether there is staggered splitting of the energy band, it can be determined whether the high-pressure phase of the candidate material has alternating magnetism.

[0029] Beneficial effects of the present invention:

[0030] 1.The application adopts a first-principle calculation method to develop high-pressure phase materials with alternating magnetism.The advantages are as follows: first, the properties of the materials can be predicted without the need for actual synthesis of the materials, thereby reducing the cost of the materials; second, in terms of time efficiency, the calculation simulation can quickly give the results, greatly improving the research and development efficiency of the alternating magnetism materials relative to the traditional experimental method; and third, the first-principle calculation software can simulate the extremely high-pressure environment that is difficult to achieve in the laboratory conditions.Therefore, using the first-principle calculation method to develop high-pressure phase materials with alternating magnetism is a practical and efficient solution.

[0031] 2.When performing the first-principle calculation, the AMS-QE software is used to optimize the structure of the material, and the AMS-BAND software is used to calculate the electronic properties of the material after the structure optimization.This calculation idea has higher efficiency relative to other material performance calculation methods.

[0032] In the embodiment of the application, the electronic properties of a plurality of phase structures of MnF2 at 0K are calculated by the first-principle calculation.It is judged that the rutile structure is the zero-pressure phase of MnF2, the SrI2 type structure and the alpha-PbCl2 type structure are high-pressure phases.The stable pressure range of the rutile structure MnF2 is about 0-4GPa, and the phase structure has alternating magnetism at zero pressure and high pressure; the stable pressure range of the SrI2 type structure is about 4-13GPa, and the high-pressure phase structure has alternating magnetism; and the stable pressure range of the alpha-PbCl2 type structure is above 13GPa, and the high-pressure phase structure has alternating magnetism. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 A flowchart of a high-pressure phase alternating magnetism material design method based on the first-principle calculation of the application;

[0034] Figure 2 A crystal model of each phase structure of MnF2 in the embodiment of the application;

[0035] Figure 3 A plurality of potential antiferromagnetic configurations of the high-pressure phase structure of MnF2 in the embodiment of the application;

[0036] Figure 4 A comparison result of the Gibbs free energy of the three phase structures at different pressures in the embodiment of the application;

[0037] Figure 5 A partial electronic band structure schematic diagram of the high-pressure phase alpha-PbCl2 type structure of MnF2 in the embodiment of the application. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and examples. All other examples obtained by those skilled in the art based on the examples in the present application belong to the scope of protection of the present application.

[0039] In the present embodiment, as shown in Figure 1 , the method is used to accurately and conveniently predict whether the MnF2 high-pressure phase has alternating magnetism, and the specific operation steps are as follows:

[0040] Step 1: Based on the multiple phase structures of MnF2, the corresponding crystal models are constructed, and the crystal model of each phase structure is as shown in Figure 2 ; the specific operation steps are as follows:

[0041] Step 1-1: By consulting the material library data, it is determined that MnF2 exists in three crystal structures at 0K, which are rutile structure, SrI2 type structure and α-PbCl2 type structure;

[0042] Step 1-2: Use AMS software to construct the crystal model of each phase structure of MnF2. The specific crystal structure information of the three phases includes the type and number of atoms, the crystal system, the space group information, the bond length and bond angle between atoms, the cell angle, the number of atoms in the cell, the cell size, the cell volume, etc.

[0043] Step 2: For each phase structure, set multiple potential antiferromagnetic configurations, and the antiferromagnetic configuration is as shown in Figure 3 ; the specific operation steps are as follows:

[0044] Step 2-1: Multiple potential antiferromagnetic configurations are set for the three phase structures, which are represented by AF1, AF2 and AF3 respectively;

[0045] Step 2-2: Set the spins of the magnetic Mn atoms to be antiparallel in the

[001] direction.

[0046] Step 3: Determine the stable antiferromagnetic configuration under the three phase structures by comparing the Gibbs free energy of AF1, AF2 and AF3 antiferromagnetic configurations under the three phase structures of MnF2; the specific operation steps are as follows:

[0047] Step 3-1: Use AMS-QE software to optimize the structure of the potential antiferromagnetic configurations AF1, AF2 and AF3 under each phase structure;

[0048] Step 3-2: Set the parameters required for structure optimization. In the present embodiment, a regular k-point grid of 10x10x10 is selected to represent the Brillouin zone for geometry optimization and single-point energy calculation; the cutoff energy is selected as 550eV; the convergence energy is set according to the requirements; U eff= U-J = 4.0 eV to deal with the strong Coulomb correlation between atoms;

[0049] Step 3-3: By comparing the Gibbs free energy of the potential anti-ferromagnetic configurations AF1, AF2 and AF3, it is determined that there is only one anti-ferromagnetic configuration of the rutile structure MnF2, which is the stable state, and the stable anti-ferromagnetic configurations of the SrI2 type structure and the α-PbCl2 type structure MnF2 are AF1 and AF3 respectively.

[0050] Step 4: Structure optimization of the three phases in the stable anti-ferromagnetic configuration, determination of the zero pressure phase and high pressure phase structure of MnF2 according to the Gibbs free energy, and obtaining the pressure range in which each phase structure stably exists, the results are shown in Figure 4 ; The specific operation steps are as follows:

[0051] Step 4-1: Use AMS-QE software to optimize the structure of the three phases in the stable anti-ferromagnetic configuration, and apply a certain range of pressure and gradually increase the pressure during optimization;

[0052] Step 4-2: Set the parameters required for structure optimization. The parameter selection is consistent with that in step 3-2 above. It should be noted that the lattice should be fixed during structure optimization to prevent lattice deformation;

[0053] Step 4-3: By comparing the relationship between the Gibbs free energy and the pressure of each phase structure, it is determined that the rutile structure is the zero pressure phase of MnF2, and the SrI2 type structure and the α-PbCl2 type structure are two high pressure phases of MnF2. The pressure range in which the rutile structure MnF2 stably exists is about 0-4 GPa; the pressure range in which the SrI2 type structure stably exists is about 4-13 GPa; and the pressure range in which the α-PbCl2 type structure stably exists is above 13 GPa.

[0054] Step 5: Electronic property calculation, the electronic band structure of MnF2 in three phase structures is obtained by first-principles calculation, the results are shown in Figure 5 ; By observing whether there is an interlaced splitting phenomenon in the energy band, it is determined whether the high pressure phases of MnF2, SrI2 type structure and α-PbCl2 type structure, have the alternating magnetic property. The specific operation steps are as follows:

[0055] Step 5-1: Use AMS-BAND software to obtain the electronic band structure of MnF2 in three phase structures by first-principles calculation;

[0056] Step 5-2: Set the electronic property calculation parameters according to specific requirements. In this embodiment, the single point calculation method is selected; U eff= UJ = 4.0 eV to account for strong interatomic Coulomb correlations; the frozen core was set to Medium; and the "unrestricted" option was selected to account for electron spin polarization. The Perdew-Burke-Ernzerhof (PBE) parameterization and the doubly polarized (DZP) basis set in the generalized-gradient approximation (GGA) were used. Spin-orbit coupling (SOC) was not selected due to its minimal effect on electronic properties.

[0057] Step 5-3: By observing the electronic band structures under the three phase structures, it is determined that the rutile structure MnF2 has alternating magnetism, the high-pressure phase - SrI2 type structure has alternating magnetism, and the high-pressure phase - α-PbCl2 type structure has alternating magnetism.

[0058] It should be pointed out that the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. Any obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for designing high-voltage phase-change magnetic materials based on first-principles calculations, characterized in that: The following steps are involved: Step 1: Based on the various phase structures of candidate antiferromagnetic materials, construct corresponding crystal models; Step 2: For each phase structure, set up multiple potential antiferromagnetic configurations; Step 3: Determine the stable antiferromagnetic configuration under each phase structure by comparing the Gibbs free energy of each potential antiferromagnetic configuration; Step 4: Optimize the structure of each phase, determine the zero-pressure phase and high-pressure phase structures of the candidate material based on the Gibbs free energy, and obtain the pressure range in which each phase structure is stable; Step 5: Calculate electronic properties. Calculate the electronic band structure of each phase of the candidate material through first-principles calculations. Observe whether the bands exhibit staggered splitting to determine whether the high-pressure phase of the candidate material exhibits alternating magnetism. In the step 1, it is specifically divided into the following steps: Step 1-1: Obtain multiple phase structures of candidate antiferromagnetic materials through literature research or based on experimental results; Step 1-2: Use AMS software to construct a crystal model of each phase structure of the candidate material; the specific crystal structure information includes the type and number of atoms, the crystal system to which it belongs, space group information, bond lengths and angles between atoms, unit cell angle, number of atoms in the unit cell, unit cell size, and unit cell volume; In the step 2, it is specifically divided into the following steps: Step 2-1: Set up multiple potential antiferromagnetic configurations based on the crystal structure; Step 2-2: Set the spin arrangement direction of the magnetic atoms as required; In the step 3, it is specifically divided into the following steps: Step 3-1: Use AMS-QE software to perform structural optimization on multiple potential antiferromagnetic configurations under each phase structure; Step 3-2: Set the parameters required for structure optimization, including the selection of high symmetry wave vector point grid, cutoff energy, and strong Coulomb correlation between atoms U eff , frozen core, whether to fix the lattice, convergence energy; Step 3-3: Determine the stable antiferromagnetic configuration under each phase structure by comparing the Gibbs free energy of each potential antiferromagnetic configuration; In the step 4, it is specifically divided into the following steps: Step 4-1: Use AMS-QE software to optimize the structure of each phase in the stable antiferromagnetic configuration, applying a certain range of pressure and gradually increasing pressure during the optimization; Step 4-2: Set the parameters required for structure optimization, including the selection of high symmetry wave vector point grid, cutoff energy, and strong Coulomb correlation between atoms U eff , freezing the core, converging energy; when optimizing the structure, the lattice needs to be fixed to prevent the lattice from deforming under high pressure; Step 4-3: Determine the zero-pressure and high-pressure phase structures of the candidate material by comparing the relationship between Gibbs free energy and pressure under each phase structure, and obtain the pressure range in which each phase structure exists stably; In the step 5, it is specifically divided into the following steps: Step 5-1: Use AMS-BAND software to calculate the electronic band structure of each phase structure of the candidate material through first-principles calculations; Step 5-2: Set the electronic properties calculation parameters according to specific needs, including the choice of calculation method, the strong Coulomb correlation effect U between atoms eff , frozen core, convergence energy, whether to consider the spin polarization behavior of electrons, parameterization and basis set selection, whether to consider spin-orbit coupling, and set other parameters according to needs; Step 5-3: By observing whether there is staggered splitting of the energy band, it is determined whether the high-pressure phase of the candidate material has alternating magnetism.

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