Method for designing rare earth ion doping regulation and control of phase change of metal oxide based on first principle

Abstract

The invention discloses a method for designing rare earth ion doping based on a first principle to regulate and control phase change of a metal oxide, relates to the field of quantitative design of materials, and aims to solve the problems of high cost and low efficiency in the aspects of screening rare earth elements, predicting a phase change path and optimizing electrical properties of an existing experimental method. The method comprises the following steps: S1, constructing super cell models with the same doping proportion and different phase structures based on the element composition of a rare earth doped metal oxide; s2, calculating the change of the total energy along with the volume for the supercell model of each phase structure; s3, fitting a curve of the total energy of each phase structure along with volume change by adopting a solid state equation to obtain phase change pressure among the phase structures; s4, making a phase diagram of phase change pressure-doping proportion; and step S5, screening out the rare earth doping proportion with ptranss = 0, namely the rare earth doping proportion of the phase change of the metal oxide. The method is used for accurately regulating and controlling the phase change and electrical properties of the metal oxide.

Description

Technical Field

[0001] The present invention relates to the field of quantitative material design, and in particular to a method for regulating metal oxide phase transition by rare earth ion doping based on first principles design. Background Art

[0002] With the rapid development of new energy and electronic devices, metal oxides have attracted considerable attention due to their unique physical and chemical properties, and hold great potential for application in solid-state electrolytes, sensors, and ferroelectric devices. Metal oxides typically exhibit a variety of phase structures (e.g., cubic, tetragonal, and monoclinic), and their complex phase transition mechanisms present challenges in precisely controlling their structural stability and electrical properties.

[0003] Research has shown that rare earth ion doping can effectively regulate the phase transition behavior of metal oxides. For example, yttrium (Y)-doped zirconium oxide (ZrO2) stabilizes the high-temperature cubic phase to medium-low temperatures while simultaneously regulating oxygen vacancies, thereby achieving a solid oxide fuel cell electrolyte material with high oxygen ion mobility. Bismuth ferrite (BiFeO3) doped with samarium (Sm) and neodymium (Nd) can form two coexisting phases with a morphotropic phase boundary, unleashing the intrinsically large ferroelectric polarization of BiFeO3 ceramics and enhancing their non-volatility in memory chips.

[0004] However, traditional experimental methods are costly and inefficient for screening rare earth elements, predicting phase transition pathways, and optimizing electrical properties, making them difficult to rapidly design for multi-component material systems. Therefore, it is necessary to develop computational methods for rare earth ion doping design to guide experiments and achieve precise control of metal oxide phase transitions and electrical properties, leading to breakthroughs in device applications. Summary of the Invention

[0005] The present invention aims to solve the problems of high cost and low efficiency of existing experimental methods in screening rare earth elements, predicting phase transition paths and optimizing electrical properties, and to provide a method for regulating metal oxide phase transition by rare earth ion doping based on first principles design.

[0006] The present invention designs a method for regulating the phase transition of metal oxides by rare earth ion doping based on first principles, comprising the following steps:

[0007] Step S1, constructing a supercell model with the same doping ratio and different phase structures based on the elemental composition of the rare earth-doped metal oxide;

[0008] Step S2, using the first-principles Quantum ESPRESSO software to calculate the variation of total energy with volume for the supercell model of each phase structure;

[0009] Step S3, using the solid state equation to fit the curve of the total energy of each phase structure versus volume to obtain the phase transition pressure between each phase structure;

[0010] Step S4, calculating the phase transition pressure under different doping ratios and making a phase diagram of phase transition pressure-doping ratio;

[0011] Step S5: Analyze the phase diagram and select p trans =0 is the rare earth doping ratio at which the metal oxide undergoes phase transition.

[0012] Furthermore, the specific method of constructing the supercell model with the same doping ratio and different phase structures in step S1 is as follows:

[0013] S11. Based on the first principles of density functional theory, a rare earth ion doping model is selected; the rare earth ion doping model is an ordered supercell model, a disordered VCA cell model, or a quasi-random structure supercell model;

[0014] S12. With the help of material crystal structure visualization software, based on the stable and metastable phases that may form under different thermodynamic conditions of metal oxides, a supercell model with the same doping ratio and different phase structures is constructed to obtain the three-dimensional atomic coordinates.

[0015] Furthermore, the material crystal structure visualization software in step S12 is Materials Studio or Xcrysden.

[0016] Furthermore, the specific method of step S2 is as follows:

[0017] S21, input three-dimensional atomic coordinates, set calculation parameters, perform geometric optimization on the supercell model, and obtain the ground state stable structure of the supercell model and its three-dimensional coordinates;

[0018] S22. Change the volume of the ground state stable structure of the supercell model, perform three-dimensional coordinate optimization and static self-consistent calculation on the supercell model, and obtain the total energy of the supercell model under different volumes.

[0019] The specific method for changing the volume of the ground state stable structure of the supercell model in step S22 is performed according to the following steps:

[0020] 1. Select several lattice compression and tension strains (η);

[0021] Second, by a'=a×(1+η), the lattice constant a of the ground state stable structure of the supercell model is changed to a', thereby changing the volume.

[0022] Furthermore, step S3 is specifically as follows:

[0023] S31. Calculate the first-order derivative of the fitted curve of total energy (E) versus volume (V) to obtain a pV curve of pressure (p) versus volume;

[0024] S32. Obtain a pH curve showing enthalpy (H) versus pressure using the formula H = E + pV;

[0025] S33, subtract the pH curves of different phase structures to obtain the p-ΔH curve, and the pressure value p corresponding to ΔH=0 trans. That is the phase transition pressure between various phase structures.

[0026] The solid state equation is the Birch-Murnaghan state equation:

[0027]

[0028] Where E represents the total energy of a phase structure supercell model, V represents the volume of the phase structure supercell model, E0 and V0 represent the total energy and total volume of the phase structure supercell model in the ground state stable structure, B0 and B0 ′ It represents the bulk modulus under the ground state stable structure of the phase structure supercell model and the first-order derivative of the bulk modulus with respect to volume.

[0029] Beneficial effects of the present invention:

[0030] The present invention uses first-principles calculations based on density functional theory (DFT) to simulate the ground state structure and electronic state density of the material, providing an efficient approach to revealing the microscopic mechanism of rare earth ion doping regulation.

[0031] 1. The present invention adopts a first-principles calculation method, which only requires the basic crystal structure information of each element in the rare earth-doped metal oxide system, without any additional experimental parameters, to calculate the atomic position, electronic state, total energy and other information of the system;

[0032] 2. The method of the present invention reveals, through calculation, how the phase structure of metal oxides changes with the ratio of rare earth ion doping, which can provide theoretical guidance and design basis for experimentally controlling the phase transition of metal oxides by rare earth ion doping and developing new material systems;

[0033] 3. The implementation of the method of the present invention only requires computer experimental equipment to carry out quantitative design of materials, which significantly reduces experimental costs and eliminates interference from complex experimental factors. The research efficiency is high and the calculation method is universal. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The ordered supercell model of cubic phase (c) and tetragonal phase (t) of rare earth ion-doped ZrO2 in Example 1, wherein the rare earth ion doping ratio is x=0.125;

[0035] Figure 2To select Y rare earth ion doping, the p-ΔH curves of t phase and c phase under the condition of doping ratio x=0.125;

[0036] Figure 3 The p-ΔH curves of the t-phase and c-phase under the condition of Sc rare earth ion doping and doping ratio x=0.125 are shown;

[0037] Figure 4 is the phase transition pressure p between t phase and c phase after selecting two different rare earth elements Y and Sc trans. With the change of doping ratio;

[0038] Figure 5 This is the XRD phase analysis spectrum of YSZ (x = 0.08) nanopowder;

[0039] Figure 6 This is the XRD phase analysis spectrum of ScSZ (x=0.1) nanopowder. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0041] Specific embodiment 1: This embodiment is based on the first principles design of a method for regulating the phase transition of metal oxides by rare earth ion doping, including the following steps:

[0042] Step S1, constructing a supercell model with the same doping ratio and different phase structures based on the elemental composition of the rare earth-doped metal oxide;

[0043] Step S2, using the first-principles Quantum ESPRESSO software to calculate the variation of total energy with volume for the supercell model of each phase structure;

[0044] Step S3, using the solid state equation to fit the curve of the total energy of each phase structure versus volume to obtain the phase transition pressure between each phase structure;

[0045] Step S4, calculating the phase transition pressure under different doping ratios and making a phase diagram of phase transition pressure-doping ratio;

[0046] Step S5: Analyze the phase diagram and select p trans =0 is the rare earth doping ratio at which the metal oxide undergoes phase transition.

[0047] This embodiment uses Quantum ESPRESSO software to calculate the total energy and volume of the rare earth ion doped oxide supercell model. Compared with similar general software, this software has simple operation, flexible parameter setting and good accuracy.

[0048] Through first-principles calculations, the correlation between the phase structure of metal oxides and rare earth ion doping was revealed, and the rare earth doping ratio with zero phase transition pressure (metal oxide undergoes phase transition) was efficiently screened out.

[0049] Specific embodiment 2: In step S1 of this embodiment, based on the elemental composition of rare earth-doped metal oxides, the specific method for constructing a supercell model with the same doping ratio and different phase structures is as follows:

[0050] S11. Based on the first principles of density functional theory, a rare earth ion doping model is selected; the rare earth ion doping model is an ordered supercell model, a disordered VCA cell model, or a quasi-random structure supercell model;

[0051] S12. Using material crystal structure visualization software, construct a supercell model with the same doping ratio and different phase structures based on the stable and metastable phases that may form under different thermodynamic conditions of the metal oxide, and obtain three-dimensional atomic coordinates. The other steps and parameters are the same as those in Specific Embodiment 1.

[0052] This embodiment takes into account the difference in valence between metal ions and rare earth ions in metal oxides and selects a corresponding rare earth ion doping model based on the constructed supercell size, thereby improving the accuracy of the simulation.

[0053] For the supercell model of N×N×N size, when N=1, the disordered VCA cell model is selected; when N≥2, the ordered supercell model or the quasi-random structure supercell model is selected.

[0054] Specific embodiment 3: In step S12 of this embodiment, the material crystal structure visualization software is Materials Studio or Xcrysden. Other steps and parameters are the same as those in specific embodiment 1 or 2.

[0055] This embodiment uses visualization software such as Materials Studio or Xcrysden to directly set the supercell model size and doping elements.

[0056] Specific embodiment 4: In step S2 of this embodiment, the specific method for calculating the change of total energy with volume for the supercell model of each phase structure using the first principles Quantum ESPRESSO software is as follows:

[0057] S21, input three-dimensional atomic coordinates, set calculation parameters, perform geometric optimization on the supercell model, and obtain the ground state stable structure of the supercell model and its three-dimensional coordinates;

[0058] S22, changing the volume of the ground state stable structure of the supercell model, performing three-dimensional coordinate optimization and static self-consistent calculation on the supercell model, and obtaining the total energy of the supercell model at different volumes. Other steps and parameters are the same as those in the first to third embodiments.

[0059] Specific embodiment 5: The specific method of changing the volume of the ground state stable structure of the supercell model in step S22 of this embodiment is carried out according to the following steps:

[0060] 1. Select several lattice compression and tension strains (η);

[0061] Second, by a'=a×(1+η), the lattice constant a of the ground state stable structure of the supercell model is changed to a', thereby changing the volume. Other steps and parameters are the same as those of the first embodiment of the first to fourth embodiments.

[0062] Specific embodiment 6: In step S3 of this embodiment, the solid state equation is used to fit the curve of the total energy of each phase structure versus volume, and the specific method for obtaining the phase transition pressure between each phase structure is as follows:

[0063] S31. Calculate the first-order derivative of the fitted curve of total energy (E) versus volume (V) to obtain a pV curve of pressure (p) versus volume;

[0064] S32. Obtain a pH curve showing enthalpy (H) versus pressure using the formula H = E + pV;

[0065] S33, subtract the pH curves of different phase structures to obtain the p-ΔH curve, and the pressure value p corresponding to ΔH=0 trans. That is, the phase transition pressure between each phase structure. Other steps and parameters are the same as those in the first to fourth embodiments.

[0066] This embodiment can ensure that the ground state stable structure of the supercell model only undergoes volume changes without changes in phase structure, thereby satisfying the application conditions of the equation of state.

[0067] Specific embodiment seven: The solid state equation in this embodiment is the Birch-Murnaghan state equation:

[0068]

[0069] Where E represents the total energy of a phase structure supercell model, V represents the volume of the phase structure supercell model, E0 and V0 represent the total energy and total volume of the phase structure supercell model in the ground state stable structure, B0 and B0 ′ The bulk modulus and the first-order derivative of the bulk modulus with respect to the volume under the ground state stable structure of the phase structure supercell model are shown in FIG. The other steps and parameters are the same as those in the first to sixth embodiments.

[0070] The following embodiments of the present invention are described in detail. The following embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation plans and specific operating processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0071] Example 1:

[0072] This embodiment takes ZrO2 as the metal oxide and yttrium (Y) ions as the rare earth doping ions as an example. By testing a specific supercell model, the influence of the rare earth ion doping ratio on the phase transition pressure is investigated, and the doping ratio with zero phase transition pressure is screened out to verify the beneficial effects of the present invention.

[0073] Step 1: Read the phase structure data of ZrO2 cubic phase (c) and tetragonal phase (t) from the crystal diffraction database or the open source database, and write the calculation input file. The unit cell crystal structure data is shown in Table 1:

[0074] Table 1

[0075]

[0076] Then, based on the elemental composition and phase structure of Y-doped ZrO2, Zr x Y 1-x O2(YSZ) supercell model. Considering the valence difference between +4 Zr ions and +3 Y ions, an ordered supercell model is selected, that is, the doping ions of each phase structure do not change the symmetry of the phase structure. In this embodiment, a c-phase and t-phase supercell containing 24 atoms are constructed for a doping ratio of x=0.125, that is, the supercell model contains 1 Y ion, 7 Zr ions and 16 O ions, as shown in FIG. Figure 1 shown.

[0077] Step 2: Using the first-principles Quantum ESPRESSO calculation software package, calculate the variation of total energy with volume for the supercell model of each phase structure.

[0078] Input the three-dimensional atomic coordinates of the c-phase and t-phase supercells of YSZ, set the calculation parameters, and perform geometric optimization on the supercell model to obtain the ground state stable structure and three-dimensional coordinates of the supercell model. Among them, the electron exchange correlation energy of each element is approximated by the LDACA-PZ functional, and the valence electrons are approximated by the plane wave pseudopotential (PAW). Before the geometric optimization of the unit cell, it is necessary to test the k-point sampling size and the total energy of the cutoff energy. In order to balance the calculation accuracy and efficiency, the total energy change <10 -3 The minimum k point and the lowest cutoff energy after eV are used as the final convergence parameters. The k point sampling interval after the test is The converged cutoff energy is 60Ry (=816eV), and the total energy error is 1.36×10 -9 eV, the maximum force constant error is The maximum atomic displacement error is

[0079] The ground-state stable structures and three-dimensional coordinates of the optimized YSZ c-phase and t-phase supercells can be used to calculate the total energy of the supercell model at different volumes.

[0080] Step 3: Select the lattice strain (η): 3%, 2%, and 1% compressive strain, and -1%, -2%, and -3% tensile strain. By using a' = a × (1 + η), b' = b × (1 + η), and c' = c × (1 + η), the lattice constants of the ground-state stable structures of the YSZ c-phase and t-phase supercell models are changed, thereby changing the volume of the ground-state stable structures of the supercell models.

[0081] Then, the three-dimensional coordinates of the supercell model of each volume are optimized and static self-consistently calculated to obtain the total energy of the supercell model at different volumes.

[0082] Step 4: Run the ev.x code in the Quantum ESPRESSO computational software package. Based on the YSZ phase structure, the Birch-Murnaghan solid state equation was used to fit the total energy versus volume curves for the YSZ c-phase and t-phase. Taking the first-order derivative of the fitted total energy (E) versus volume (V) curve yielded a pV curve, representing the pressure (p) versus volume. Using the formula H = E + pV, a pH curve was obtained, representing the enthalpy (H) versus pressure.

[0083] Then, the pH curves of different c-phase and t-phase are subtracted to obtain the p-ΔH curve. The pressure value p corresponding to ΔH=0 is trans. =-3.86GPa, which is the phase transition pressure between the c-phase and t-phase of YSZ when the doping ratio x=0.125, as shown in Figure 2 shown.

[0084] Step 5: Select a Y ion doping ratio of x = 0.0625. Based on the symmetry of the c-phase and t-phase, construct a c-phase and t-phase supercell containing 48 atoms, respectively. That is, the supercell model contains 1 Y ion, 15 Zr ions, and 32 O ions. Repeat steps 2, 3, and 4 to obtain the phase transition pressure between the c-phase and t-phase of YSZ at a doping ratio of x = 0.0625.

[0085] Step 6: Based on the phase transition pressure at the doping ratio of x = 0.0625 and x = 0.125, a phase diagram of YSZ phase transition pressure-doping ratio is drawn, as shown in Figure 4 As shown. Analyze the phase diagram and screen out ptrans. = 0 (metal oxide phase change) rare earth doping ratio is x Y =0.0675.

[0086] Example 2:

[0087] The difference between this embodiment and embodiment 1 is that the rare earth doping ions are scandium (Sc) ions. The other steps and parameters are the same as those in embodiment 1. The phase transition pressure between the c-phase and t-phase of ScSZ at the doping ratio of x = 0.125 is as follows: Figure 3 As shown, p trans. =-18.98GPa; the phase diagram of ScSZ phase transition pressure-doping ratio is as follows Figure 4 As shown. Analyze the phase diagram and screen out p trans. =0 rare earth doping ratio is x Sc =0.0583.

[0088] To verify the above examples 1 and 2, YSZ nanopowders with a doping ratio of x = 0.08 and ScSZ nanopowders with a doping ratio of x = 0.1 were synthesized by the sol-gel method. Samples calcined at 700°C, 750°C, and 800°C were selected for X-ray diffraction (XRD) phase characterization. Figure 5 and Figure 6 As shown in the analysis of diffraction peaks, it can be seen that under the above doping ratio, the crystal structure of the nanopowders obtained at the three calcination temperatures is cubic phase, which is consistent with Figure 4 Prediction results of the phase diagram.

[0089] In summary, the present invention first constructs supercell models of different phase structures under the same doping ratio based on the elemental composition of rare earth doped metal oxides. Secondly, the variation of total energy with volume of the supercell models of each phase structure is calculated by the first-principle Quantum ESPRESSO calculation software package. Thirdly, the solid state equation is used to fit the curve of the total energy variation with volume of each phase structure to obtain the phase transition pressure between each phase structure. Finally, the phase transition pressure under different doping ratios is calculated, and a phase diagram of phase transition pressure-doping ratio is made. The phase diagram is analyzed to screen out the p trans. = 0 (metal oxide phase transition). This invention clarifies the relationship between the rare earth ion doping ratio and the phase transition pressure of metal oxides, playing a positive role in the research of developing metal oxides with specific phase structures. The screening method is based on first-principles density functional calculations. The screening object is a rare earth-doped metal oxide supercell model. The rare earth doping ratio is used as a variable to examine the effect of this variable on the stability of different phase structures.

Claims

1. A method for regulating metal oxide phase transition by rare earth ion doping based on first principles design, characterized in that: The method comprises the following steps: Step S1, constructing a supercell model with the same doping ratio and different phase structures based on the elemental composition of the rare earth-doped metal oxide; Step S2, using the first-principles Quantum ESPRESSO software to calculate the variation of total energy with volume for the supercell model of each phase structure; Step S3, using the solid state equation to fit the curve of the total energy of each phase structure versus volume to obtain the phase transition pressure between each phase structure; Step S4, calculating the phase transition pressure under different doping ratios and making a phase diagram of phase transition pressure-doping ratio; Step S5: Analyze the phase diagram and select p trans =0 is the rare earth doping ratio at which the metal oxide undergoes phase transition.

2. The method for controlling metal oxide phase transition by rare earth ion doping based on first principles design according to claim 1, characterized in that: The specific method of constructing a supercell model with the same doping ratio and different phase structures based on the elemental composition of the rare earth-doped metal oxide in step S1 is as follows: S11. Select the rare earth ion doping model based on the first principles of density functional theory; S12. With the help of material crystal structure visualization software, based on the stable and metastable phases that may form under different thermodynamic conditions of metal oxides, a supercell model with the same doping ratio and different phase structures is constructed to obtain the three-dimensional atomic coordinates.

3. The method of controlling metal oxide phase transition by rare earth ion doping based on first principles design according to claim 2, characterized in that: The rare earth ion doping model is an ordered supercell model, a disordered VCA cell model or a quasi-random structure supercell model.

4. A method for regulating metal oxide phase transition by rare earth ion doping based on first principles design according to claim 2 or 3, characterized in that: The material crystal structure visualization software in step S12 is Materials Studio or Xcrysden.

5. The method of controlling metal oxide phase transition by rare earth ion doping based on first principles design according to claim 1, characterized in that: The specific method for calculating the variation of total energy with volume for the supercell model of each phase structure using the first-principles Quantum ESPRESSO software in step S2 is as follows: S21, input three-dimensional atomic coordinates, set calculation parameters, perform geometric optimization on the supercell model, and obtain the ground state stable structure of the supercell model and its three-dimensional coordinates; S22. Change the volume of the ground state stable structure of the supercell model, perform three-dimensional coordinate optimization and static self-consistent calculation on the supercell model, and obtain the total energy of the supercell model under different volumes.

6. The method for controlling metal oxide phase transition by rare earth ion doping based on first principles design according to claim 5, characterized in that: The specific method for changing the volume of the ground state stable structure of the supercell model in step S22 is performed according to the following steps:

1. Select several lattice compression and tension strains η; Second, by a'=a×(1+η), the lattice constant a of the ground state stable structure of the supercell model is changed to a', thereby changing the volume.

7. The method of controlling metal oxide phase transition by rare earth ion doping based on first principles design according to claim 1, characterized in that: In step S3, the solid state equation is used to fit the curve of the total energy of each phase structure versus volume to obtain the phase transition pressure between each phase structure. The specific method is as follows: S31. Calculate the first-order derivative of the fitted curve of total energy (E) versus volume (V) to obtain a pV curve of pressure (p) versus volume; S32. Obtain a pH curve showing enthalpy (H) versus pressure using the formula H = E + pV; S33, subtract the pH curves of different phase structures to obtain the p-ΔH curve, and the pressure value p corresponding to ΔH=0 trans. That is the phase transition pressure between various phase structures.

8. The method for controlling metal oxide phase transition by rare earth ion doping based on first principles design according to claim 7, characterized in that: The solid state equation is the Birch-Murnaghan state equation: Where E represents the total energy of a phase structure supercell model, V represents the volume of the phase structure supercell model, E0 and V0 represent the total energy and total volume of the phase structure supercell model in the ground state stable structure, B0 and B0 ′ It represents the bulk modulus under the ground state stable structure of the phase structure supercell model and the first-order derivative of the bulk modulus with respect to volume.

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