Method for screening formation energy of equimolar-ratio spinel-type high-entropy oxide

Abstract

The invention discloses a method for screening formation energy of equimolar-ratio spinel-type high-entropy oxide. The method comprises the following steps: 1) acquiring substrate crystal information; 2) acquiring space coordinates of a substrate crystal; (3) making a fully combined POSCAR file; (4) a corresponding POTCAR is manufactured; 5) high-flux first principle calculation; 6) calculating monatomic average formation energy; 7) a monatomic average formation energy table; 8) extrapolating hexabasic spinel formation energy; according to the method, the formation energy of the six-element high-entropy spinel can be estimated, the huge calculation cost of the first principle of six-element large unit cells can be omitted, elements occupying the site A and the site B which are beneficial to stable existence of the spinel type high-entropy oxide can be quickly screened out, and element combinations which can stably exist can be screened out.

Description

Technical Field

[0001] The invention relates to material technology, in particular to a method for screening formation energy of spinel-type high entropy oxides of equal molar ratio. Background Art

[0002] Spinel (AB 2 O 4 The spinel structure allows many different cations to be stably miscible and has a high cation diversity. This diversity makes the spinel structure have scalable chemical variability, which in turn provides great flexibility in functional design; high entropy oxides (HEOs) have high thermal stability, stable crystal structure, unique geometric compatibility and electronic structure, both of which have aroused considerable scientific interest among scientists and technicians. Spinel high entropy oxides (Sp-HEOs) are both spinel configurations and high entropy single-phase solid solutions. It is easy to create many new phases by adjusting the type and fraction of components, providing new strategies for the development of new materials with new technology-related properties.

[0003] However, currently, although there are first-principles calculations of various properties of spinel-type binary oxides in major databases, there is almost no data available for ab initio calculation of enthalpy convex hulls for high-entropy oxides. It is uncertain whether the formation energy of six-component high-entropy oxides composed of certain elements can be used to screen the spinel-type high-entropy oxides under their combination, and it is uncertain which element occupies the A site and which element occupies the B site is conducive to the stable existence of spinel-type high-entropy oxides. Summary of the invention

[0004] The purpose of the present invention is to provide a method for screening the formation energy of spinel-type high entropy oxides of equal molar ratio in view of the deficiencies of the prior art. This method can estimate the formation energy of hexavalent high entropy spinel, and can avoid the huge calculation cost of first-principles calculation of hexavalent large unit cells, and can quickly screen out which elements occupying the A site and the B site are conducive to the stable existence of spinel-type high entropy oxides; and screen out which element combinations can exist stably.

[0005] The technical solution for achieving the purpose of the present invention is:

[0006] A method for screening the formation energy of spinel-type high entropy oxides of equal molar ratio comprises the following steps:

[0007] 1) Obtain substrate crystal information: Download the binary spinel FeCo crystal database from the Materials Project 2 O 4 Crystal structure file, get about {AB 2 O 4The atomic arrangement regularity information of spinel type is the atomic arrangement information of Pd-3m crystal space group in Cubic crystal system;

[0008] 2) Obtain the spatial coordinates of the substrate crystal: Based on the crystal structure file obtained from the crystal database, the cif file of a binary crystal structure obtained by the vaspkit plug-in is used to obtain the atomic coordinates of the spinel type - the specific three-dimensional coordinates of Fe, Co, and O elements in the lattice. Taking the substrate FeCo2O4 crystal as an example, the lattice coordinates of 8 Fe atoms, 16 Co atoms, and 32 oxygen atoms, a total of 56 atoms, are obtained, and then converted into a POSCAR file in the vasp file format;

[0009] 3) Make a fully combined POSCAR file: Enumerate all possible combinations to replace the base FeCo 2 O 4 The binary metal atoms in the structure, namely Fe atoms and Co atoms, are used to make the POSCAR crystal structure information file of the full row combination, where the ranges of A and B elements are from: {Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Ba, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi};

[0010] 4) Make the corresponding POTCAR: Based on the POSCAR crystal structure information file in step 3), make the POTCAR pseudopotential file corresponding to each combination, and the pseudopotential adopts the self-projection augmented plane wave method PAW_PBE;

[0011] 5) High-throughput first-principles calculations: Use VASP software to perform high-throughput structural optimization in first-principles calculations on all input files in the entire set of binary spinels and each combination, so that the total system energy of each combination reaches the lowest equilibrium state;

[0012] 6) Calculate the average formation energy of a single atom: The ground state energy E in the OSZICAR file of one of the first-principles calculation result files of each binary spinel is converted into 0 Extract, and then according to the formula:

[0013]

[0014] Calculate the average formation energy E of a single atom in the spinel unit cell f , where E A 、E B 、E O2are expressed as the ground state total energy of a single A-site atom, a single B-site atom, and an oxygen molecule, respectively, n A 、n B and n O2 are the number of A-site atoms, B-site atoms and oxygen atoms in the unit cell respectively; N is the total number of atoms in the unit cell,

[0015] Based on FeCo 2 O 4 Taking FeCo crystal as an example, 2 O 4 The average formation energy of a single atom is:

[0016]

[0017] Thus, CoFe is rotated symmetrically 2 O 4 Crystals have:

[0018]

[0019] And so on, the average total energy under each combination is calculated;

[0020] 7) Single atom average formation energy table: According to the single atom average formation energy, an atom-to-atom formation energy table is made. 2 O 4 And the symmetric combination CoFe 2 O 4 When it comes to crystals, the value of the Fe row and Co column in the number table is -1.0386125, and then the value of the symmetrical Co row and Fe column is -1.036905714, and so on, to make an atom-to-atom value table. Since the hexavalent spinel high entropy oxide can be obtained from a variety of binary spinels in one-step phase transition fusion, and the formation energy before and after the reaction is unchanged, the linear combination of the binary atom-to-atom formation energy value table is used to extrapolate the formation energy of the hexavalent high entropy spinel oxide;

[0021] 8) Extrapolation of the hexavalent spinel formation energy: Select two metals at site A and four metals at site B, then find the corresponding 8 grids in the table obtained in step 7), sum them, and then average them as Eavg8, then the average value of the 36 grids where the six metal elements are located is recorded as Eavg36, and Δh = Eavg8-Eavg36. If Δh < 0, then this selection method has a lower formation energy. Take Cu, Ni, Al, Cr, Fe, and Co as examples: Consider (Cu 4 Ni 4 ) 1 [Al 2 Cr 2 Fe 2 Co2 ] 2 O 32 When this composition is used, the corresponding 8 grids are: Cu row Al column, Cu row Cr column, Cu row Fe column, Cu row Co column, Ni row Al column, Ni row Cr column, Ni row Fe column, Ni row Co column, and the row priority indicates the element occupying the A site. (Cu 4 Ni 4 ) 1 [Al 2 Cr 2 Fe 2 Co 2 ] 2 O 32 The formation energy is represented by the average value Eavg8 of the above 8 grids; when more elements occupy the A site, [Cu 6 Ni 6 Al 6 Cr 6 Fe 6 Co 6 ] 2 (Cu 6 Ni 6 Al 6 Cr 6 Fe 6 Co 6 ) 36 ——The general molecular formula of both is equimolar spinel oxide, both are Cu 0.5 Ni 0.5 Al 0.5 Cr 0.5 Fe 0.5 Co 0.5 The 36 grids corresponding to O are: Cu row and Cu column, Cu row and Ni column...Cu row and Co column, Ni row and Cu column, Ni row and Ni column...Ni row and Co column, Al row..., Cr row..., Fe row..., Co row..., the average value of the above 36 grids is Eavg36, which means [Cu 6 Ni 6 Al 6 Cr 6 Fe 6 Co 6 ] 2 (Cu 6 Ni 6 Al 6 Cr 6 Fe 6 Co 6 ) 36 The formation energy of

[0022] 9) Cluster analysis: Perform clustering classification for machine learning based on Δh, and use the cluster.KMeans function in the skitlearn library in Python to block-screen all element sets.

[0023] This technical solution uses the first principles to calculate the formation energy of binary spinel to extrapolate the formation energy of hexavalent spinel, which can roughly estimate the formation energy of hexavalent high-entropy spinel and avoid the huge computational cost of first principles calculation of hexavalent large unit cells. On this basis, it can quickly screen out which elements occupying the A site and the B site are conducive to the stable existence of spinel-type high-entropy oxides; screen out which element combinations can exist stably. The extrapolation method uses binary data points to infer the hexavalent values ​​outside the data range. It is assumed that the known binary local phase can be periodically extended to the region. In fact, it cannot accurately describe the random distribution of multiple cations in the hexavalent high-entropy oxide, and does not take into account the influence of the lattice distortion of the hexavalent high-entropy oxide on the formation energy. However, as a screening method for elements occupying the A and B sites, it is sufficient to summarize it with the trend of the extrapolation method.

[0024] This method can estimate the formation energy of hexavalent high-entropy spinel, and can avoid the huge computational cost of first-principles calculations of hexavalent large unit cells. It can quickly screen out which elements occupying the A site and B site are conducive to the stable existence of spinel-type high-entropy oxides; and screen out which element combinations can exist stably. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of a method flow chart of an embodiment;

[0026] Figure 2 Schematic diagram of cluster analysis in the embodiment. DETAILED DESCRIPTION

[0027] The content of the present invention is further described below in conjunction with the drawings and embodiments, but the present invention is not limited thereto.

[0028] Example:

[0029] Reference Figure 1 , a method for screening the formation energy of spinel-type high entropy oxides of equal molar ratio, comprising the following steps:

[0030] 1) Obtain substrate crystal information: Download the binary spinel FeCo crystal database from the Materials Project 2 O 4 Crystal structure file, get about {AB 2 O 4 The atomic arrangement regularity information of spinel type is the atomic arrangement information of Pd-3m crystal space group in Cubic crystal system;

[0031] 2) Obtain the spatial coordinates of the substrate crystal: Based on the crystal structure file obtained from the crystal database, the cif file of a binary crystal structure obtained by the vaspkit plug-in is used to obtain the atomic coordinates of the spinel type - the specific three-dimensional coordinates of Fe, Co, and O elements in the lattice. Taking the substrate FeCo2O4 crystal as an example, the lattice coordinates of 8 Fe atoms, 16 Co atoms, and 32 oxygen atoms, a total of 56 atoms, are obtained, and then converted into a POSCAR file in the vasp file format;

[0032] 3) Make a fully combined POSCAR file: Enumerate all possible combinations to replace the base FeCo 2 O 4 The binary metal atoms in the structure, namely Fe atoms and Co atoms, are used to make the POSCAR crystal structure information file of the full row combination, where the ranges of A and B elements are from: {Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Ba, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi};

[0033] 4) Make the corresponding POTCAR: Based on the POSCAR crystal structure information file in step 3), make the POTCAR pseudopotential file corresponding to each combination, and the pseudopotential adopts the self-projection augmented plane wave method PAW_PBE;

[0034] 5) High-throughput first-principles calculations: Use VASP software to perform high-throughput structural optimization in first-principles calculations on all input files in the entire set of binary spinels and each combination, so that the total system energy of each combination reaches the lowest equilibrium state;

[0035] 6) Calculate the average formation energy of a single atom: The ground state energy E in the OSZICAR file of one of the first-principles calculation result files of each binary spinel is converted into 0 Extract, and then according to the formula:

[0036]

[0037] Calculate the average formation energy E of a single atom in the spinel unit cell f , where E A 、E B 、E O2 are expressed as the ground state total energy of a single A-site atom, a single B-site atom, and an oxygen molecule, respectively, n A 、n B and n O2are the number of A-site atoms, B-site atoms and oxygen atoms in the unit cell respectively; N is the total number of atoms in the unit cell. 2 O 4 Taking FeCo crystal as an example, 2 O 4 The average formation energy of a single atom is:

[0038]

[0039] Thus, CoFe is rotated symmetrically 2 O 4 Crystals have:

[0040]

[0041] And so on, the average total energy under each combination is calculated;

[0042] 7) Single atom average formation energy table: According to the single atom average formation energy, an atom-to-atom formation energy table is made. 2 O 4 And the symmetric combination CoFe 2 O 4 When the crystal is formed, the value of the Fe row and Co column in the numerical table is -1.0386125, and then the value of the symmetrical Co row and Fe column is -1.036905714, and so on, to make an atom-to-atom numerical table. Since the hexavalent spinel high entropy oxide can be obtained from a variety of binary spinels in one-step phase transition fusion, and the formation energy before and after the reaction is unchanged, the linear combination of the binary atom-to-atom formation energy numerical table is used to extrapolate the formation energy of the hexavalent high entropy spinel oxide;

[0043] 8) Extrapolation of the hexavalent spinel formation energy: Select two metals at site A and four metals at site B, then find the corresponding 8 grids in the table obtained in step 7), sum them, and then average them as Eavg8, then the average value of the 36 grids where the six metal elements are located is recorded as Eavg36, and Δh = Eavg8-Eavg36. If Δh < 0, then this selection method has a lower formation energy. Take Cu, Ni, Al, Cr, Fe, and Co as examples: Consider (Cu 4 Ni 4 ) 1 [Al 2 Cr 2 Fe 2 Co 2 ] 2 O 32When this composition is used, the corresponding 8 grids are: Cu row Al column, Cu row Cr column, Cu row Fe column, Cu row Co column, Ni row Al column, Ni row Cr column, Ni row Fe column, Ni row Co column, and the row priority indicates the element occupying the A site. (Cu 4 Ni 4 ) 1 [Al 2 Cr 2 Fe 2 Co 2 ] 2 O 32 The formation energy is represented by the average value Eavg8 of the above 8 grids; when more elements occupy the A site, [Cu 6 Ni 6 Al 6 Cr 6 Fe 6 Co 6 ] 2 (Cu 6 Ni 6 Al 6 Cr 6 Fe 6 Co 6 ) 36 ——The general molecular formula of both is equimolar spinel oxide, both are Cu 0.5 Ni 0.5 Al 0.5 Cr 0.5 Fe 0.5 Co 0.5 The 36 grids corresponding to O are: Cu row and Cu column, Cu row and Ni column...Cu row and Co column, Ni row and Cu column, Ni row and Ni column...Ni row and Co column, Al row..., Cr row..., Fe row..., Co row..., the average value of the above 36 grids is Eavg36, which means [Cu 6 Ni 6 Al 6 Cr 6 Fe 6 Co 6 ] 2 (Cu 6 Ni 6 Al 6 Cr 6 Fe 6 Co 6 ) 36 The formation energy of

[0044] 9) Cluster analysis: Based on Δh, cluster classification for machine learning is performed. The cluster.KMeans function in the skitlearn library in Python is used to filter all element sets in blocks, such as Figure 2 As shown, in this example, cluster analysis Figure 2 In the example, the range of elements comes from 3d elements: {Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga}. When n_cluster, i.e. the number of cluster categories, is 64, the silhouette_score function value under the silhouette coefficient distribution map based on the cluster distribution map label reaches a minimum value (calling the silhouette function: fromsklearn.metrics import silhouette_samples, silhouette_score), and the target performance is screened: a set of elements with a small delta and a small formation energy of a six-element combination - then the corresponding cluster element set is cluster number 42, 9, 59. If the performance is a large Δh and a large formation energy, the corresponding cluster set is number 51, 53, 57. Then count the number of occurrences of elements in numbers 51, 53, and 59, and select the elements with the highest number of occurrences according to the number of occurrences of each 3d element. Here, the top few elements with the largest expected impact on the target oxide formation energy and Δh are selected when two elements are selected at the A site.

Claims

1. A method for screening the formation energy of spinel-type high entropy oxides in equal molar ratio, characterized in that: The steps include: 1) Obtaining substrate crystal information: Downloading the binary spinel FeCo2O4 crystal structure file from the Materials Project crystal database, obtaining the atomic arrangement regularity information of the {AB2O4} spinel type, i.e., the atomic arrangement information of the Pd-3m crystal space group in the Cubic crystal system; 2) Obtaining the spatial coordinates of the substrate crystal: Based on the crystal structure file obtained from the crystal database, the cif file of a binary crystal structure obtained by the vaspkit plug-in is used to obtain the atomic coordinates of the spinel type, and then converted into a POSCAR file in the vasp file format; 3) Make a fully combined POSCAR file: enumerate all possible combinations to replace the binary metal atoms, namely, Fe atoms and Co atoms, in the substrate FeCo2O4 structure to make a fully combined POSCAR crystal structure information file, where the ranges of A and B elements are from: {Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Ba, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi}; 4) Make the corresponding POTCAR: Based on the POSCAR crystal structure information file in step 3), make the POTCAR pseudopotential file corresponding to each combination, and the pseudopotential adopts the self-projection augmented plane wave method PAW_PBE; 5) High-throughput first-principles calculations: Use VASP software to perform high-throughput structural optimization in first-principles calculations on all input files in the entire set of binary spinels and each combination, so that the total system energy of each combination reaches the lowest equilibrium state; 6) Calculate the average formation energy of a single atom: Extract the ground state energy E0 from the OSZICAR file, one of the first-principles calculation result files of each binary spinel, and then use the formula: Calculate the average formation energy E of a single atom in the spinel unit cell f , where E A 、E B 、E O2 are expressed as the ground state total energy of a single A-site atom, a single B-site atom, and an oxygen molecule, respectively, n A 、n B and n O2 are the number of A-site atoms, B-site atoms and oxygen atoms in the unit cell respectively; N is the total number of atoms in the unit cell. The average formation energy of a single atom of FeCo2O4 is: Therefore, the CoFe2O4 crystal has the following rotation symmetry: And so on, the average total energy under each combination is calculated; 7) Single atom average formation energy table: According to the single atom average formation energy, an atom-to-atom formation energy table is prepared. When calculating the base FeCo2O4 and the symmetrical combination CoFe2O4 crystal, the value of the Fe row and Co column in the table is selected as -1.0386125, and then the value of the symmetrical Co row and Fe column is -1.036905714. By analogy, an atom-to-atom table is prepared. Since the hexavalent spinel high entropy oxide can be obtained from a variety of binary spinels in one-step phase transition fusion, and the formation energy before and after the reaction is unchanged, the formation energy of the hexavalent high entropy spinel oxide is extrapolated based on the linear combination of the binary atom-to-atom formation energy table; 8) Extrapolation of the hexavalent spinel formation energy: Select two metals at site A and four metals at site B, then find the corresponding eight grids in the table obtained in step 7), sum them, and then average them as Eavg8. Then the average value of the 36 grids where the six metal elements are located is recorded as Eavg36. Δh = Eavg8-Eavg36. If Δh < 0, then this selection method has a lower formation energy. Cu, Ni, Al, Cr, Fe, Co six elements (Cu4Ni4)1[Al2Cr2Fe2Co2]2O 32 When composed, the corresponding 8 grids are: Cu row and Al column, Cu row and Cr column, Cu row and Fe column, Cu row and Co column, Ni row and Al column, Ni row and Cr column, Ni row and Fe column, Ni row and Co column. The row priority indicates the element occupying the A site, (Cu4Ni4)1[Al2Cr2Fe2Co2]2O 32 The formation energy can be expressed as the average value Eavg8 of the above 8 grids; when more elements occupy the A site, [Cu6Ni6Al6Cr6Fe6Co6]2(Cu6Ni6Al6Cr6Fe6Co6)O 36 ——The general molecular formula of both is equimolar spinel oxide, both are Cu 0.5 Ni 0.5 Al 0.5 Cr 0.5 Fe 0.5 Co 0.5 O——The corresponding 36 grids are: Cu row Cu column, Cu row Ni column...Cu row Co column, Ni row Cu column, Ni row Ni column...Ni row Co column, Al row..., Cr row..., Fe row..., Co row..., the average value of the above 36 grids is Eavg36, which means [Cu6Ni6Al6Cr6Fe6Co6]2(Cu6Ni6Al6Cr6Fe6Co6)O 36 The formation energy of 9) Cluster analysis: Perform clustering classification for machine learning based on Δh, and use the cluster.KMeans function in the skitlearn library in Python to block-screen all element sets.

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