Method for regulating photoelectric property of two-dimensional Janus material based on first principle and strain

Abstract

The invention provides a method for regulating and controlling the photoelectric property of a two-dimensional Janus material based on a first principle and strain, and relates to the technical field of two-dimensional photoelectric material application, and the method is characterized in that VESTA and VASP are used for calculation, and then a material capable of improving the photoelectric property through strain is screened out. The method comprises the following specific steps: extracting a two-dimensional Janus material from a database, carrying out structural design, and converting a. Cif file into a. Vasp file format; performing structural relaxation on the material, and performing static self-consistent calculation; on the basis of parameter modification in S2, photoelectric property calculation is conducted on the stable material; and applying positive strain and negative strain to the material, repeating the step when the strain is not applied, calculating the state density, the energy band structure light absorption coefficient and the carrier mobility of the material, and comparing the property of the material after the strain is applied with the property of the material without the strain. According to the method, chemical substances are not needed in the whole implementation process, environmental pollution is avoided, time is saved, and meanwhile cost is saved.

Description

Technical Field

[0001] The present invention relates to the technical field of two-dimensional optoelectronic material applications, and in particular to a method for regulating the optoelectronic properties of two-dimensional Janus materials based on first principles and strain. Background Art

[0002] Two-dimensional (2D) materials have attracted great attention due to the successful isolation of graphene. However, the zero band gap of graphene limits its wide application. Two-dimensional materials with band gaps, such as silicene, phosphorene, hexagonal boron nitride (h-BN), transition metal dichalcogenides (MX2: M = Mo, W; X = S, Se, Te) and IV-VI compounds, have been gradually studied due to their remarkable optoelectronic properties.

[0003] Some two-dimensional materials with mirror symmetry can construct double-sided materials by replacing atoms on one side. The resulting new structure is called Janus structure. At present, two-dimensional Janus materials such as MoSSe, MoSTe, WSeTe, VSSe, PdSSe, InGaSSe, SnSSe, etc. have been synthesized experimentally. The inherent asymmetry of Janus materials leads to a suitable energy gap, resulting in special electrical, optical and other physical properties. For example, Kahraman Z. et al. studied the properties of monolayer HTaSe2 and FTaSe2 and found that atomic functionalization will cause the energy band near the Fermi level to shift to a lower energy and produce a metal-semiconductor transition. The two-dimensional Janus NiSSe monolayer exhibits significant optical response in the infrared, visible and ultraviolet spectral ranges. JanusMoSO and MoSSe structures have high light absorption coefficients in the far-infrared region and also have good absorption of near-ultraviolet and far-ultraviolet light.

[0004] At the same time, experimentally, the goal of regulating the electronic and optical properties of materials can be achieved by applying strain engineering to materials. For example, Sun Chuying et al. demonstrated a strain engineering method induced by nanoimprinting, which can produce three-dimensional adjustable strain in two-dimensional materials and lead to periodic changes in strain. Strain has multiple effects on the structure, electronic properties and optical properties of materials. Chuan He et al. found that uniaxial strain destroys the in-plane symmetry of two-dimensional materials, such as WS2 monolayer. Chen Weiquan et al. applied strain to MoS2 and found that strain would cause the crystal symmetry to be destroyed and the spectrum to red shift. Thanh et al. have demonstrated that strain engineering can significantly change the light absorption of γ-GeX (X=S, Se, Te) in the visible light region. At present, research on applying biaxial strain to two-dimensional Janus materials still requires a lot of theoretical data to provide theoretical calculations for experiments. Summary of the invention

[0005] The purpose of the present invention is to solve the technical problem that there is a lack of research methods for applying biaxial strain to two-dimensional Janus materials in the prior art.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for regulating the photoelectric properties of two-dimensional Janus materials based on first principles and strain, wherein the method uses VESTA and VASP to perform calculations and then screen out materials that can enhance the photoelectric properties through strain.

[0008] Preferably, the specific steps are as follows:

[0009] S1: Material extraction and structural design:

[0010] Extract the .cif file of the two-dimensional Janus material from the database, perform structural design on the two-dimensional Janus material, and convert the structural data file type into the .vasp file format;

[0011] S2: Structural optimization: structural relaxation of the two-dimensional material monolayer constructed in S1 and static self-consistent calculation;

[0012] S3: Property calculation: Based on the parameter modification of S2, calculate the photoelectric properties of stable materials;

[0013] S4: In-plane biaxial strain is applied to the a-axis and b-axis of the material, and the band structure, state density, light absorption coefficient and carrier mobility of the two-dimensional Janus material monolayer under different degrees of strain are calculated using VASP software, and the materials without strain and with strain are compared.

[0014] Preferably, in S1, VESTA visual structure drawing software is used to perform structural design on some two-dimensional Janus materials to convert the structure data file type into a .vasp file format.

[0015] Preferably, in S2, the conjugate gradient algorithm is used to perform structural optimization on the lattice parameters and atomic coordinates of the two-dimensional Janus material, the INCAR setting parameters are ISIF=3, IBRION=2, and the K point in the KPOINTS file is set to 15×15×1.

[0016] Preferably, the static self-consistent calculation in S3 is performed using a data structure after the stable structure is obtained and converged.

[0017] Preferably, the INCAR parameters are modified on the basis of static self-consistency in S3, the photoelectric properties are calculated using the Perdew–Burke–Ernzerhof (PBE) method to obtain a stable band structure, state density and light absorption coefficient, and origin is used to analyze and plot the data of state density, band structure and light absorption coefficient.

[0018] Preferably, the strain applied in S4 ranges from -8% to 8%.

[0019] The present application provides a method for regulating the photoelectric properties of two-dimensional Janus materials based on first principles and strain. By calculating and regulating two-dimensional Janus materials, the influence of strain on different properties of materials can be quickly understood, and two-dimensional Janus materials with improved photoelectric properties under strain can be screened out. The method of the present invention does not require chemicals in the overall implementation process, does not pollute the environment, saves time and costs. In addition, the present invention is simple and fast to operate, easy to use, and has high repeatability and accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 FIG. 1 is a structural diagram of a γ-Sn2OSe single layer in one embodiment of the present invention, wherein (a) is a top view,

[0021] (b) is a side view;

[0022] Figure 2 Density of states diagram of γ-Sn2OSe under different strains.

[0023] Figure 3 Figure 2 is the light absorption coefficient diagram of γ-Sn2OSe under different strains, where (a) is compressive strain and (b) is tensile strain. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with specific embodiments.

[0025] A method for regulating the photoelectric properties of two-dimensional Janus materials based on first principles and strain, wherein the method uses VESTA and VASP to perform calculations and then screen out materials that can enhance the photoelectric properties through strain.

[0026] Specifically, the method comprises the following steps:

[0027] S1: Material extraction and structural design:

[0028] In one embodiment, a .cif file of a two-dimensional Janus material is extracted from a database, a structure design of a portion of the two-dimensional Janus material is performed using VESTA visual structure drawing software, and the structure data file type is converted into a .vasp file format;

[0029] In one embodiment, the two-dimensional Janus material extracted from the database is a material film, and the vacuum layer is set to The initial structure, lattice parameters and atomic arrangement positions were obtained. The structural data file type was converted from .cif to .vasp file format with the help of VASTA software and renamed POSCAR for preliminary structural relaxation.

[0030] S2: Structural Optimization:

[0031] Specifically, in one embodiment, the VASP software program is used to perform structural relaxation on the preliminarily constructed two-dimensional material monolayer using a conjugate gradient algorithm, and after a stable structure is obtained and converged, a static self-consistent calculation is performed using the data structure after structural optimization;

[0032] In one embodiment, the step 2 uses a conjugate gradient algorithm to optimize the lattice parameters and atomic coordinates of the two-dimensional Janus material, the INCAR setting parameters are ISIF=3, IBRION=2, and the K point in the KPOINTS file is set to 15×15×1, and static calculation is performed when the optimized structure reaches the convergence standard. Among them, the INCAR parameters are set to ISIF=2, IBRION=-1, NSW=0, and the K point in the KPOINTS file is set to 20×20×1.

[0033] S3: Property calculation:

[0034] Based on S2, INCAR and KPOINTS parameters are modified to calculate the photoelectric properties of stable materials, such as energy band, state density, and light absorption coefficient;

[0035] In one embodiment, the S3 modifies the INCAR parameters based on static self-consistency, uses the Perdew–Burke–Ernzerhof (PBE) method to calculate the photoelectric properties, obtains a stable band structure, state density and light absorption coefficient, and uses origin to analyze and plot the data of state density, band structure and light absorption coefficient.

[0036] S4: Strain application

[0037] Apply in-plane biaxial strain to the a-axis and b-axis of the material, with the strain range from -8% to 8%, and use VASP software to calculate the band structure, state density, light absorption coefficient and carrier mobility of the two-dimensional Janus material monolayer under different degrees of strain. Compare the materials without strain and after strain.

[0038] Specifically, the strain degree is -8%, -6%, -4%, -2%, 2%, 4%, 6% and 8%, and the steps of S2 and S3 are repeated to calculate the structural optimization, static self-consistency, band structure, state density, light absorption coefficient and carrier mobility of the strained two-dimensional Janus material. Among them, ISIF=2 in the INCAR parameter.

[0039] The above contents are described below in conjunction with specific embodiments:

[0040] Step 1: Material selection:

[0041] The two-dimensional Janus material γ-Sn2OSe was selected as the substrate. As an asymmetric two-dimensional Janus material, γ-Sn2OSe has a hexagonal structure and four atomic layers, which are O atoms, Sn atoms and Se atoms from top to bottom.

[0042] Step 2: γ-Sn2OSe structure design:

[0043] The crystal was preliminarily constructed using VESTA visual structure drawing software to obtain the preliminary geometric structure of γ-Sn2OSe with a structure file type of .cif, and the structure data file type was converted into a .vasp file format;

[0044] Step 3: Structural optimization:

[0045] The VASP software program was used to perform structural relaxation on the initially constructed two-dimensional Janus material γ-Sn2OSe. After convergence, the optimized data structure was used for static self-consistent calculations.

[0046] Step 3.1, use the conjugate gradient algorithm to optimize the structure of γ-Sn2OSe and obtain the optimized file CONTCAR. Among them, the lattice parameters of γ-Sn2OSe are The Sn-Se bond length is The Sn-O bond length is The VASP software has an energy cutoff of 500 eV for plane waves and a force threshold of The unit cell energy threshold is 1×10 7 eV. The K points in the KPOINTS file are set to 15×15×1.

[0047] Step 3.2, rename the optimized CONTCAR file to POSCAR file as the structure file for subsequent static calculations to achieve the minimum energy of the system. The unit cell energy threshold is 1×10 7 eV, the K point in the KPOINTS file is set to 20×20×1.

[0048] Step 4: Property calculation:

[0049] After the static self-consistent calculation is completed, the INCAR parameters are modified on the basis of the static self-consistent calculation, and the photoelectric properties are calculated using the Perdew–Burke–Ernzerhof (PBE) method.

[0050] Step 5: Apply strain:

[0051] Apply in-plane biaxial strain to the a-axis and b-axis of γ-Sn2OSe, and the strain degrees are -8%, -6%, -4%, -2%, 2%, 4%, 6% and 8%. According to steps 3 and 4, the structural optimization, static self-consistency, band structure, state density, light absorption coefficient and carrier mobility of γ-Sn2OSe after strain are calculated. Among them, ISIF = 2.

[0052] Figure 1 This is the structural diagram of γ-Sn2OSe single-layer crystal from different perspectives. γ-Sn2OSe has a sandwich structure with four atomic layers, which are O atoms, Sn atoms and Se atoms from top to bottom.

[0053] Figure 2 The state density diagram of γ-Sn2OSe under different strains is given. It can be seen that the band gap of γ-Sn2OSe decreases as the strain value increases under positive or negative strain. The band gap is 1.32 eV when no strain is applied. After applying 8% strain, the band gap does not change significantly, but when -8% strain is applied, the band gap shrinks to 0.44 eV.

[0054] Figure 3 The light absorption coefficient diagram of γ-Sn2OSe under different strains is given. It can be seen that the absorption rate of γ-Sn2OSe in the near red part of visible light and the near purple part of visible light decreases and increases with the increase of strain, respectively, regardless of whether it is under compressive strain or tensile strain. In the infrared and ultraviolet bands, the absorption changes little with the increase of strain.

[0055] In combination with the above specific embodiments, the present application provides a method for regulating the photoelectric properties of two-dimensional Janus materials based on first principles and strain. By calculating and regulating two-dimensional Janus materials, the influence of strain on different properties of materials can be quickly understood, and two-dimensional Janus materials with improved photoelectric properties under strain can be screened out. The method of the present invention does not require chemicals in the overall implementation process, does not pollute the environment, saves time and costs. In addition, the present invention is simple and fast to operate, easy to use, and has high repeatability and accuracy.

Claims

1. A method for regulating the photoelectric properties of two-dimensional Janus materials based on first principles and strain, characterized by: The method uses VESTA and VASP to perform calculations and screen out materials that can enhance optoelectronic properties through strain.

2. The method for regulating the photoelectric properties of two-dimensional Janus materials based on first principles and strain according to claim 1, characterized in that: The specific steps are as follows: S1: Material extraction and structural design: Extract the .cif file of the two-dimensional Janus material from the database, perform structural design on the two-dimensional Janus material, and convert the structural data file type into the .vasp file format; S2: Structural optimization: structural relaxation of the two-dimensional material monolayer constructed in S1 and static self-consistent calculation; S3: Property calculation: Based on the parameter modification of S2, calculate the photoelectric properties of stable materials; S4: In-plane biaxial strain is applied to the a-axis and b-axis of the material, and the band structure, state density, light absorption coefficient and carrier mobility of the two-dimensional Janus material monolayer under different degrees of strain are calculated using VASP software, and the materials without strain and with strain are compared.

3. The method for regulating the photoelectric properties of two-dimensional Janus materials based on first principles and strain according to claim 2, characterized in that: In S1, VESTA visual structure drawing software is used to perform structural design on some two-dimensional Janus materials to convert the structural data file type into a .vasp file format.

4. The method for regulating the photoelectric properties of two-dimensional Janus materials based on first principles and strain according to claim 3, characterized in that: In S2, the conjugate gradient algorithm is used to optimize the lattice parameters and atomic coordinates of the two-dimensional Janus material. The INCAR parameters are set to ISIF=3, IBRION=2, and the K point in the KPOINTS file is set to 15×15×1.

5. The method for regulating the photoelectric properties of two-dimensional Janus materials based on first principles and strain according to claim 4, characterized in that: The static self-consistent calculation in S3 is performed using the data structure after the structure optimization after the stable structure is obtained and converged.

6. The method for regulating the photoelectric properties of two-dimensional Janus materials based on first principles and strain according to claim 5, characterized in that: The INCAR parameters are modified on the basis of the static self-consistency in S3, and the photoelectric properties are calculated using the Perdew–Burke–Ernzerhof (PBE) method to obtain stable band structures, state density and light absorption coefficients. Origin is used to analyze and plot the data of state density, band structure and light absorption coefficient.

7. The method for regulating the photoelectric properties of two-dimensional Janus materials based on first principles and strain according to claim 6, characterized in that: The strain applied in S4 ranges from -8% to 8%.

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