A screening method and device for piezoelectric anisotropic perovskite materials

Abstract

The application discloses a screening method and device of piezoelectric anisotropic perovskite material, and high-throughput calculation and screening are performed on tetragonal phase ABO3 perovskite oxide material through first principle calculation, the correlation between piezoelectricity and lattice tetragonality, polarization displacement, spontaneous polarization and elastic constant is pointed out, and the method can be used for screening and guiding design of high-performance piezoelectric material. The application gives a three-dimensional representation of piezoelectric coefficient, re-evaluates the piezoelectric coefficient ratio |d 33 / d 31 | which is widely used at present, and points out the deficiency in representing piezoelectric anisotropy, and can be extended to anisotropy of other piezoelectric materials.

Description

Technical Field

[0001] This invention relates to the calculation and simulation of piezoelectric anisotropy of perovskite materials, and more particularly to a method and apparatus for screening piezoelectric anisotropic perovskite materials. Background Technology

[0002] Over the past century, functionalized ABO3-type oxide perovskite materials have been extensively studied due to their superior ferroelectric and piezoelectric properties resulting from spontaneous polarization. Switchable polarization enables applications in fields such as ferroelectric information technology, while piezoelectric conversion of mechanical and electrical energy is fundamental in several important technologies, including ultrasonic transducers and actuators. The piezoelectricity of the latter, as a third-order tensor, involves a complex coupling between heat, mechanical quantities, and electrical quantities described by thermodynamics.

[0003] Piezoelectric transducers are widely used in many fields such as ultrasonic medical diagnostics, industrial non-destructive testing, hydrophones, and transformers. With the rapid development of ultrasonic technology, higher demands are placed on the performance of materials used in piezoelectric transducers. These demands require the highest possible thickness electromechanical coupling coefficient and piezoelectric anisotropy to ensure full coupling between the transducer and the medium without parasitic mode interference, more concentrated energy in the thickness mode, high sensitivity and resolution, and smaller device miniaturization. The key to achieving high-performance piezoelectric transducers is the development of piezoelectric ceramic materials with excellent piezoelectric properties and high anisotropy.

[0004] The tetragonal phase of ABO3 perovskites is particularly important in various structures. In experiments, most piezoelectric responses and large ferroelectric polarizations occur in the tetragonal phase or its mixtures (Thomann, H. Piezoelectric ceramics. Advanced Materials 2, 458-463 (1990)). This invention focuses on the piezoelectric anisotropy of the P4mm tetragonal phase, which is crucial for modern engineering applications such as ultrasonic transducers and robotic metamaterials. Highly anisotropic materials can provide minimal noise and increased operating frequencies from transverse vibrations, significantly reducing manufacturing costs by bypassing precise control of thickness resonant modes. Although its importance was recognized in the 1990s, the intrinsic factors controlling piezoelectric anisotropy, such as composition and geometry, remain unclear for the extensively studied P4mm phase of ABO3 materials. Elucidating these underlying mechanisms will contribute to the design of highly anisotropic piezoelectric materials and the explanation of anomalous properties near morphophase boundaries and nonpolar directions.

[0005] For most perovskites, experimental piezoelectric data are largely lacking. Furthermore, the reported values ​​vary considerably due to different measurement temperatures (Liang, L., Li, Y., Hu, SY, Chen, L.-Q. & Lu, G.-H. Piezoelectric anisotropy of aKNbO3 single crystal. Journal of Applied Physics 108 (2010).), techniques (Kalinichev, A., Bass, J., Sun, B. & Payne, D. Elastic properties of tetragonal PbTiO3 single crystals by Brillouin scattering. Journal of Materials Research 12, 2623-2627 (1997).), and sample size effects (Majdoub, M., Sharma, P. & Cagin, T. Enhanced size-dependent piezoelectricity and elasticity in nanostructures due to the flexoelectric effect. Physical Review B 77, 125424 (2008).).

[0006] Therefore, there is an urgent need for an efficient and standardized method for the screening and design of piezoelectric anisotropic materials. Summary of the Invention

[0007] This invention provides a screening method for piezoelectric anisotropic perovskite materials, which solves the problem that existing technologies have large differences in piezoelectric data values ​​due to different measurement temperatures, techniques, and sample size effects. This method can screen out a series of strongly piezoelectric anisotropic perovskite materials, saving expensive experimental trial and error costs.

[0008] The technical solution of the present invention is as follows:

[0009] A method for screening piezoelectric anisotropic perovskite materials includes the following steps:

[0010] (1) Remove unsuitable compounds from the ABO3 compounds in the Materials Project database; A and B are metallic elements, and O is oxygen.

[0011] (2) Extract the symmetry and Wyckoff position of all crystal phases in the compound database that meet the requirements, and screen out ABO3 compounds that have crystal phases that meet the requirements of perovskite symmetry and Wyckoff position.

[0012] (3) Extract the electronic structure band gap (E) of the screened ABO3 compounds. g Information was used to screen out ABO3 compounds with a crystal phase containing Eg > 0.1 eV;

[0013] (4) Construct cubic and tetragonal perovskite structures for the ABO3 compounds screened in step (3), perform structural relaxation, and obtain information on the energy, electronic structure band gap and lattice parameters of the crystal phase.

[0014] (5) Select phases that satisfy the condition that the energy of the tetragonal phase is less than that of the cubic phase (E). t <E c ), lattice parameter c / a ratio > 1.01 and electronic structure band gap E of tetragonal phase g Tetragonal ABO3 compounds with a voltage greater than 0.1 eV;

[0015] (6) Density functional perturbation theory calculations were performed on the selected tetragonal ABO3 compounds to obtain their elastic constant tensor C, piezoelectric constant tensor e, and Born effective charge tensor.

[0016] (7) Based on the elastic constant tensor C, select the system that meets the mechanical stability requirements of tetragonal perovskite from the selected tetragonal ABO3 compounds;

[0017] (8) Perform data analysis on the tetragonal ABO3 compounds with mechanical stability selected in step (7) to obtain a three-dimensional representation of their piezoelectric anisotropy, and select tetragonal ABO3 compounds that meet the requirements of piezoelectric anisotropy; fit the phase diagram, analyze the factors that determine the strength of piezoelectric anisotropy, and use it to predict or design materials with high piezoelectric anisotropy.

[0018] In step (1), the non-compliant compounds include: compounds containing the elements H, B, Si, C, N, P, I, Br, F, Cl, S, Se and Te, as well as compounds with Energy Above Hull (energy relative to the phase decomposition reaction) > 1 eV / atom.

[0019] Energy Above Hull is defined as the normalized energy of each atom above a linear combination of stable equilibrium phases of a component in a phase diagram. It represents the energy required for a phase decomposition reaction. The smaller the Energy Above Hull, the more stable the phase and the easier it is to synthesize experimentally.

[0020] In step (2), the perovskite symmetry and Wyckoff position matching require that the compound has at least one crystal form that simultaneously satisfies the space group and its corresponding element Wyckoff position in Table 1:

[0021] Table 1

[0022]

[0023] In step (4), structural relaxation is performed using the VASP software package until the energy and force convergence accuracy is reached. The energy convergence accuracy is typically 10. -6 eV, the convergence accuracy of force is typically 10. -3 .

[0024] In step (6), density functional perturbation theory calculations are carried out using the VASP software package.

[0025] In steps (4) and (6), the cutoff energy in the VASP software package is uniformly set to 550 eV, the ion energies all converge to below 0.005 eV, the k-point of the Brillouin zone is 8×8×6, and the functional is PBEsol.

[0026] In step (7), the criteria for determining whether the mechanical stability requirements of tetragonal perovskite are met are as follows:

[0027]

[0028] Among them, C ij Let i and j be the tensor elements of the elastic constant tensor C, respectively. ij The row and column numbers.

[0029] In step (8), the polarization displacement mode amplitude Where α is the index of the ion in the unit cell, Δr α This represents the displacement of the ion from its centrally symmetrical position.

[0030] Spontaneous polarization P through Born effective charge tensor The following was obtained from the calculation of the ion displacement Δr:

[0031]

[0032] Where Ω is the unit cell volume, α is the index of the ion in the unit cell, and m is the index of the coordinate system.

[0033] This invention employs high-throughput first-principles calculations for a comprehensive study, designed to accelerate time-consuming growth and characterization experiments. A holistic picture can be obtained through valuable insights into structural distortions, chemical properties, polarization, and elastic properties, and their relationship to piezoelectric anisotropy.

[0034] Based on the same inventive concept, the present invention also provides a screening device for piezoelectric anisotropic perovskite materials, including a computer memory, a computer processor, and a computer program stored in the computer memory and executable on the computer processor. When the computer processor executes the computer program, it implements the steps of the above-described screening method for piezoelectric anisotropic perovskite materials.

[0035] Compared with the prior art, the beneficial effects of the present invention are:

[0036] By employing high-throughput calculations based on first-principles calculations, perovskite oxide materials with strong piezoelectric anisotropy can be designed, predicted, and screened. Using symmetry, Wyckoff position matching, band gap, and mechanical stability criteria, ABO3 candidate materials that are easily synthesized experimentally can be theoretically and efficiently screened. Then, this invention uses density functional perturbation theory to calculate the piezoelectric properties of ABO3 materials, screening and predicting a series of high-piezoelectric anisotropy perovskite oxide materials, providing theoretical guidance for experimental synthesis and verification, effectively reducing experimental R&D costs and shortening the R&D cycle. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the process for high-throughput computational screening and prediction of high-voltage anisotropic perovskites according to an embodiment of the present invention.

[0038] Figure 2 Schematic diagrams of the cubic and tetragonal phases of ABO3 perovskite and the elemental distribution at the A and B sites of the screened perovskite system.

[0039] Figure 3 The energy distribution and polarization shift mode amplitude distribution of the ABO3 perovskite structure in this embodiment of the invention; (a) the energy difference (E) between the tetragonal phase (lattice constant fixed at P4mm phase) and the cubic phase. t -E c (a) is a function of c / a for the tetragonal phase; (b) is the energy difference (E) between the tetragonal P4mm phase and the cubic phase. t -E c (c) shows the relationship between the displacement amplitude and the interatomic displacement amplitude; (d) shows the distribution of displacement amplitude and Goldschmidt tolerance factor relative to the c / a ratio, with the pentagon highlighting the five experimentally synthesized P4mm perovskites; (e) shows the plane charge density of conventional tetragonal phase BaTiO3 (BTO) and supertetragonal phase BiCoO3 (BCO), respectively.

[0040] Figure 4The spontaneous polarization properties of the candidate material system in the embodiments of the present invention are shown in (a) as the relationship between polarization (P) and interatomic displacement amplitude; (b) as the relationship between polarization P and c / a ratio; and (c) as the polarization contribution of A site, B site and O ion as a function of c / a ratio.

[0041] Figure 5 The elastic anisotropy of the candidate material system in the embodiments of the present invention is shown in (a)-(c), where the elastic constant is a function of the c / a ratio; and (d) is a three-dimensional representation of the Young's modulus of five experimental P4mm perovskites.

[0042] Figure 6 The piezoelectric anisotropy of the candidate material system in the embodiments of the present invention is shown in (a)-(c), which are the piezoelectric coefficients d, respectively. 33 and d 31 ,|d 33 / d 31 |and|e 33 / e 31 The relationship between |d| and c / a ratio; (d) is |d| 33 / d 31 | and d 31 The negative correlation; (e)-(g) are the piezoelectric coefficients d of PbTiO3(PTO), respectively. 33 and d 31 The three-dimensional representation; (f)-(h) are the piezoelectric coefficients d of P4mm BiCoO3(BCO), respectively. 33 and d 31 A three-dimensional representation; where d 33 The three-dimensional surface represents the piezoelectric response values ​​in different longitudinal stress directions; in the Marmier method, d 31 The solid three-dimensional surface represents the minimum piezoelectric response under the longitudinal stress direction (due to different transverse stress directions), while the transparent surface represents the maximum piezoelectric response under the longitudinal stress direction. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not limit it in any way.

[0044] This invention provides a computational method for screening perovskite materials with high piezoelectric anisotropy, saving expensive experimental trial-and-error costs and solving the problem of poor performance of existing piezoelectric anisotropic materials. Figure 1 As shown, it includes the following steps:

[0045] Step 1: Evaluate all more than 140,000 ABO3 compounds in the Materials Project material database (including those that have been experimentally synthesized and those that are purely theoretically predicted). Among them, A and B are mainly metal elements, and O is oxygen. First, preliminarily screen out compounds containing elements H, B, Si, C, N, P, I, Br, F, Cl, S, Se, and Te, and then further screen out compounds with an Energy Above Hull (energy relative to the phase decomposition reaction) > 1 eV / atom. A total of 988 potential ABO3 perovskite compounds are screened out.

[0046] Step 2: Extract the symmetries and Wyckoff positions of all crystal phases existing in the database of these 988 ABO3 compounds, and screen out 825 ABO3 compounds with crystal phases that meet the perovskite symmetry and Wyckoff position requirements.

[0047] The perovskite symmetry and the elemental Wyckoff position matching require that the compound has at least one crystal phase that simultaneously meets the space groups and their corresponding Wyckoff positions in Table 1.

[0048] Table 1

[0049]

[0050] Step 3: Based on the structures obtained in Step 2, extract the electronic structure band gap (E g ) information of these 825 compounds, and screen out 284 ABO3 compounds with crystal phases where E g > 0.1 eV.

[0051] Step 4: Based on the structures obtained in Step 3, construct cubic (cubic) and tetragonal (tetragonal) perovskite structures for these 284 ABO3 compounds. Through the first-principles VASP calculation software package, perform structure relaxation until the energy and force convergence accuracies are reached. The energy convergence accuracy is generally 10 -6 eV, and the force convergence accuracy is generally 10 -3 , and obtain information such as energy, electronic structure band gap, and lattice parameters.

[0052] ABO3 oxide perovskite includes a cubic phase (space group ) and a tetragonal phase (space group P4mm). The ferroelectric cubic phase represents the high-temperature phase of most perovskites, and lattice distortion occurs when cooled to room temperature. The lattice parameters of the cubic phase are a = b = c, while the lattice constants of the tetragonal phase are a = b < c, where the c / a ratio of the lattice constant is widely used to quantify the lattice tetragonality of the latter.

[0053] Step 5: Screen out those that meet the condition that the energy of the tetragonal phase is less than the energy of the cubic phase (Et <E c ), lattice parameter c / a ratio > 1.01 (c and a are lattice parameters in different directions) and tetragonal phase electronic structure band gap E g There are 149 systems with a voltage greater than 0.1 eV.

[0054] Step 6: The VASP software package is used to perform density functional perturbation calculations on these 149 tetragonal ABO3 perovskites to obtain their elastic constant tensor C, piezoelectric constant tensor e, and Born effective charge tensor Z.

[0055] The elastic constant tensor C is a fourth-order tensor, under P4mm symmetry, and in Voigt notation:

[0056]

[0057] S is the inverse matrix of C, i.e., S = C -1 This is often referred to as the flexibility tensor. Correspondingly, the elastic constant tensor C is often referred to as the stiffness tensor.

[0058] The piezoelectric tensor is a third-order tensor. Experimentally, two types of piezoelectric tensors with different definitions are commonly used: the piezoelectric stress tensor *e* and the piezoelectric strain tensor *d*. Under P4mm symmetry and Voigt notation, the piezoelectric stress tensor *e* and the piezoelectric strain tensor *d* have the following forms:

[0059]

[0060]

[0061] Where e represents the response of polarization P to strain η, or the response of stress σ to electric field ε, and its tensor element e αj It can be obtained through the following relationship:

[0062]

[0063] And d represents the response of polarization P to stress ε, or the response of strain η to electric field ε, and its tensor element d αj It can be obtained through the following relationship:

[0064]

[0065] They can be converted to each other through the following relationships:

[0066] e αj =C jk d αk ,

[0067] d αj =S jk e αk .

[0068] Among them, C jk and S jk These are the tensor elements of the elastic stiffness tensor and the elastic flexibility tensor, respectively.

[0069] Step 7: By analyzing the elastic constant tensors of these 149 tetragonal ABO3 perovskites, 127 systems that meet the mechanical stability requirements of tetragonal perovskites were selected. The criteria for meeting the mechanical stability requirements of tetragonal perovskites are as follows:

[0070]

[0071] Among them, C ij Let i and j be the tensor elements of the elastic constant tensor C, respectively. ij The row and column numbers.

[0072] Step 8: Data processing is performed on the 127 tetragonal ABO3 perovskite species finally selected: the correlation between their piezoelectric coefficients and lattice tetragonality (i.e., the c / a ratio of the lattice parameter), polarization displacement u, spontaneous polarization P, and elastic constants is analyzed, and a three-dimensional representation of their piezoelectric anisotropy (i.e., the change of piezoelectric response with direction) is given. A phase diagram is fitted, and the factors determining the strength of piezoelectric anisotropy are analyzed, which can be used to predict and design materials with high piezoelectric anisotropy.

[0073] P4mm phase ABO3 polarization displacement mode amplitude Where α is the index of the ion in the unit cell, Δr α This represents the displacement of the ion from its centrally symmetrical position.

[0074] Spontaneous polarization P was calculated using the Born effective charge tensor Z and ion displacement Δr:

[0075]

[0076] Where Ω is the unit cell volume, α is the index of the ion in the unit cell, and m is the index of the coordinate system.

[0077] In steps 4 and 6, the cutoff energy in the VASP software package is uniformly set to 550 eV, the ion energies all converge to below 0.005 eV, the Brillouin zone k-point is 8×8×6, and the functional is PBEsol.

[0078] The process of performing calculations using the VASP software package is as follows:

[0079] (1) Prepare the input files INCAR, POSCAR, POTCAR and KPOINTS for VASP, perform structural relaxation to obtain a stable structure, and output it in the CONTCAR file. You can obtain the structural information, lattice parameters, c / a and ion displacement Δr.

[0080] (2) Based on the obtained stable structure, perform self-consistent calculations and output charge density and electronic structure information;

[0081] (3) Calculate the elastic constant C using density functional perturbation theory ij piezoelectric coefficient e αj and Born effective charge tensor The results are output in the OUTCAR file. Finally, the formula is used. To determine the magnitude of the spontaneous polarization value P, use the formula d αj =S jk e αk The piezoelectric strain tensor d is obtained αj .

[0082] The most commonly used method for representing the three-dimensional anisotropy of piezoelectric response is the axial surface method:

[0083] An axial stress σ perpendicular to the surface direction a is applied to an infinitesimal longitudinal surface. The polarization P perpendicular to the surface is given by P = dσ', where d physically represents the polarization response caused by a unit stress parallel to a. When the axial stress changes from the original direction a to a', the response value in that direction, i.e., the longitudinal surface value, becomes d'(a'), expressed in terms of the piezoelectric coefficient d 33 For example, it can be written as:

[0084] d′ 333 =a 3i a 3j a 3k d ijk .

[0085] The above equation uses Einstein's summation form, where a ij Let be the direction cosine of the axial stress. Besides d... 33 and e 33 This piezoelectric coefficient, which depends only on axial stress (a direction), is similar to that of d. 31 and e 31 The piezoelectric coefficient also depends on the radial stress (b direction), such as d. 31 The variation of with stress direction can be obtained from the following formula:

[0086] d′ 311 =a 3i b 1j b 1k d ijk ,

[0087] Where b ij Let be the direction cosine of the radial stress.

[0088] Example

[0089] The tools used in this embodiment are mainly Python scripts, shell scripts, and the Vienna ab initioSimulation Package (VASP). The primary calculation tool is VASP, and the main post-processing tools are Python-based plotting scripts and the Visualization for Electronic and Structural Analysis (VESTA) visualization tool. The specific processing of the VASP output files is as follows: the system's energy is extracted from the OUTCAR file, and Python is used to plot material energy data charts, charge density maps, and density of states maps.

[0090] This embodiment takes five experimentally synthesized tetragonal lattice ABO3 perovskites with P4mm phase as examples to provide a method for batch calculation of piezoelectric anisotropy, screening and predicting perovskite materials with high piezoelectric anisotropy.

[0091] The elastic constants and structural properties of the five experimentally synthesized tetragonal lattice ABO3 perovskites are shown in Tables 2 and 3, respectively. Table 3 includes the lattice constant a (unit: ), c / a ratio and interatomic displacement amplitude u (unit: The spontaneous polarization P (unit: μC / cm) is also listed. 2 and piezoelectric constant d 33 d 31 (Unit: pC / N) and their ratios |d 33 / d 31 |

[0092] Table 2: Elastic constants of five experimentally synthesized tetragonal lattice ABO3 perovskites

[0093]

[0094] Table 3: Structural characteristics of five experimentally synthesized tetragonal lattice ABO3 perovskites

[0095]

[0096] The method of the present invention includes the following steps:

[0097] Step 1: Evaluate the quantity of ABO3 perovskites in the database. Perovskite structures are as follows: Figure 2 As shown, this includes ideal cubic phases (space group) ) and tetragonal phases (P4 / mmm and P4mm). The ferroelectric cubic phase represents the high-temperature phase of most perovskites and undergoes distortion upon cooling to room temperature. The P4 / mmm phase only involves lattice deformation with lattice constants a = b < c, known as lattice tetragonality. The c / a ratio is widely used to quantify this tetragonality.

[0098] Step 2: As shown in the Figure 1 flowchart, candidate material systems that are experimentally easy to synthesize are screened according to symmetry matching, bandgap value size, atomic occupancy matching, and mechanical stability criteria. Then, lattice relaxation is performed on them to obtain stable structural information, self-consistent calculations to obtain charge density, atomic orbitals, and density of states, magnetic and other information, and density functional perturbation theory calculations to obtain information such as the elastic constant matrix and piezoelectric coefficient matrix of the candidate materials; it is worth mentioning that the screening strategy of the present invention has successfully identified all five experimentally crystallized P4mm perovskites: non-magnetic BaTiO3, KNbO3, and PbTiO3, as well as antiferromagnetic BiCoO3 and PbVO3.

[0099] Step 3: Analyze the structural instability and distribution characteristics of the candidate material systems. As shown in Figure 3 the relationship between the lattice tetragonality c / a, the intensity of the unstable mode, and the energy difference between the two tetragonal phases of 127 ABO3 materials.

[0100] Step 4: Analyze the spontaneous polarization properties of the candidate material systems. Figure 4 is a graph of the polarization P versus the amplitude of the atomic displacement. Graphs of the polarization and the contributions of the A-site, B-site, and O ions as a function of the c / a ratio.

[0101] Step 5: Analyze the elastic anisotropy of the candidate material systems. Figure 5 shows the variation of the elastic constants as a function of the c / a ratio and the distribution characteristics of the Young's modulus of 5 experimentally synthesized perovskites.

[0102] Step 6: Piezoelectric anisotropy analysis. Figure 6 shows the relationship between the piezoelectric coefficient, piezoelectric anisotropy, and the c / a ratio.

[0103] The present invention performs high-throughput calculations on P4mm ABO3 perovskites to comprehensively clarify the underlying mechanism that controls the intrinsic piezoelectric anisotropy by different chemical and physical factors. The calculated data show that there are two types of perovskites with significant characteristics in the perovskite system: conventional tetragonal perovskites (c / a ratio < 1.15) and super-tetragonal perovskites (c / a ratio > 1.15). They exhibit significantly different properties in terms of ferroelectric conversion barrier, polarization, elasticity, and piezoelectricity. The polarization of conventional tetragonal perovskites is mainly driven by the polarization displacement of the B-site, while that of super-tetragonal perovskites is jointly driven by the polarization displacements of the A- and B-sites. The polarization saturation and piezoelectric response suppression that occur in super-tetragonal perovskites are caused by the limit of the charge transfer, which also leads to high d in perovskites.33 Compared with the large piezoelectric anisotropy ratio |d 33 / d 31 The existence of an intrinsic contradiction exists between them. The polarization axis and the elastic softening direction together determine the maximum longitudinal piezoelectric response d. 33 Direction. The former plays a major role in determining the direction of the maximum longitudinal piezoelectric response, while the polarization axis direction plays a secondary role. This invention re-evaluates the currently widely used piezoelectric coefficient ratio |d 33 / d 31 The shortcomings in representing piezoelectric anisotropy need to be carefully considered in the multi-scale modeling of piezoelectric anisotropic devices. For most perovskites, the piezoelectric coefficient is greater than |d 33 / d 31 | cannot strictly represent piezoelectric anisotropy. The piezoelectric coefficient is less than |d 33 / d 31 | It can be used to represent piezoelectric anisotropy only when the maximum piezoelectric response is along the polarization direction (e.g., in BTO or PTO).

[0104] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for screening piezoelectric anisotropic perovskite materials, characterized in that, Includes the following steps: (1) Remove unsuitable compounds from the ABO3 compounds in the Materials Project database; A and B are metallic elements, and O is oxygen. (2) Extract the symmetry and Wyckoff position of all crystal phases in the compound database that meet the requirements, and screen out ABO3 compounds that have crystal phases that meet the requirements of perovskite symmetry and Wyckoff position. (3) Extract the electronic structure band gap E of the screened ABO3 compounds. g Information was used to screen out ABO3 compounds with a crystal phase containing Eg > 0.1 eV; (4) Construct cubic and tetragonal perovskite structures for the ABO3 compounds screened in step (3), perform structural relaxation, and obtain information on the energy, electronic structure band gap and lattice parameters of the crystal phase. (5) Screening for electronic structure band gaps E that satisfy the following conditions: tetragonal phase energy is less than cubic phase energy, lattice parameter c / a ratio > 1.01, and tetragonal phase. g Tetragonal ABO3 compounds with a phase >0.1 eV; (6) Density functional perturbation theory calculations were performed on the selected tetragonal ABO3 compounds to obtain their elastic constant tensor C, piezoelectric constant tensor e, and Born effective charge tensor. (7) Based on the elastic constant tensor C, select the system that meets the mechanical stability requirements of tetragonal perovskite from the selected tetragonal ABO3 compounds; (8) Perform data analysis on the tetragonal ABO3 compounds with mechanical stability selected in step (7) to obtain a three-dimensional representation of their piezoelectric anisotropy, and select tetragonal ABO3 compounds that meet the requirements of piezoelectric anisotropy; fit the phase diagram, analyze the factors that determine the strength of piezoelectric anisotropy, and use it to predict or design materials with high piezoelectric anisotropy.

2. The screening method for piezoelectric anisotropic perovskite materials according to claim 1, characterized in that, In step (1), the non-compliant compounds include: compounds containing elements H, B, Si, C, N, P, I, Br, F, Cl, S, Se and Te, as well as compounds with Energy Above Hull greater than 1 eV / atom.

3. The screening method for piezoelectric anisotropic perovskite materials according to claim 1, characterized in that, Perovskite symmetry and Wyckoff position matching require that the compound has at least one crystallographic isomorphism that simultaneously satisfies the space group and its corresponding element Wyckoff position in Table 1: Table 1 4. The screening method for piezoelectric anisotropic perovskite materials according to claim 1, characterized in that, In step (4), structural relaxation is performed using the VASP software package until the energy and force convergence accuracy is reached. The energy convergence accuracy is typically 10. -6 eV, the convergence accuracy of force is typically 10. -3 In step (6), density functional perturbation theory calculations are carried out using the VASP software package.

5. The screening method for piezoelectric anisotropic perovskite materials according to claim 4, characterized in that, In the VASP software package, the cutoff energy is uniformly set to 550 eV, the ion energies all converge to below 0.005 eV, the Brillouin zone k-point is 8×8×6, and the functional is PBEsol.

6. The screening method for piezoelectric anisotropic perovskite materials according to claim 1, characterized in that, In step (7), the criteria for determining whether the mechanical stability requirements of tetragonal perovskite are met are as follows: Among them, C ij Let i and j be the tensor elements of the elastic constant tensor C, respectively. ij The row and column numbers.

7. The screening method for piezoelectric anisotropic perovskite materials according to claim 1, characterized in that, In step (8), the polarization displacement mode amplitude Where α is the index of the ion in the unit cell, Δr α This represents the displacement of the ion from its centrally symmetrical position. Spontaneous polarization P through Born effective charge tensor The following was obtained from the calculation of the ion displacement Δr: Where Ω is the unit cell volume, α is the index of the ion in the unit cell, and m is the index of the coordinate system.

8. A screening device for piezoelectric anisotropic perovskite materials, characterized in that, The method includes a computer memory, a computer processor, and a computer program stored in the computer memory and executable on the computer processor, wherein the computer processor executes the computer program to implement the steps of the screening method for piezoelectric anisotropic perovskite materials as described in any one of claims 1-7.

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