Method for predicting Se vacancy infrared nonlinear optical response in few-layer PtSe2

Abstract

The invention discloses a method for predicting Se vacancy infrared nonlinear optical response in few-layer PtSe2, and the method comprises the following steps: S1, constructing a few-layer PtSe2 model, and carrying out the in-plane expansion; s2, introducing Se vacancy into the model after cell expansion; s3, performing structural relaxation on the Se-containing vacancy structure until atomic force and energy converge; s4, calculating an electron energy band structure of the relaxed structure based on a density functional theory; s5, constructing a maximum localization Wannier function, and fitting the electron energy band structure obtained in the step S4; s6, calculating an in-plane nonlinear displacement current component of the few-layer PtSe2 in an infrared band; and S7, analyzing the change of the nonlinear displacement current component obtained in the step S6 in the infrared band, and predicting the influence of Se vacancy on the infrared nonlinear optical property. The infrared nonlinear optical property prediction method provided by the invention is low in cost and high in precision.

Description

Technical Field

[0001] This invention belongs to the field of materials simulation technology, specifically relating to a method for predicting the infrared nonlinear optical response of Se vacancies in few-layer PtSe2. Background Technology

[0002] Two-dimensional PtSe2 exhibits significant application value in the field of novel optoelectronic devices due to its unique band structure and infrared photoelectric response characteristics. Modulating its nonlinear optical properties by introducing defects is currently a research hotspot, with Se vacancies being a common intrinsic defect type in PtSe2.

[0003] Currently, the experimental preparation and characterization of the nonlinear optical properties of few-layer PtSe2 suffer from problems such as high cost and limited accuracy. Furthermore, in terms of theoretical prediction, no effective method for assessing the influence of Se vacancies has been established, making it difficult to guide the defect engineering design of infrared photodetectors.

[0004] Despite significant progress in the performance of infrared photodetectors through materials and device engineering, the precise design and performance control of defect engineering, especially the active utilization of critical defects such as selenium vacancies, still faces a severe challenge due to a lack of theoretical guidance. The mechanism by which defects affect the material remains unclear: Selenium vacancies, as a common and unavoidable intrinsic defect in narrow bandgap semiconductors, lack a quantitative or semi-quantitative universal model for their specific impact on carrier concentration, mobility, recombination lifetime, and optical absorption coefficient. Existing research largely focuses on experimental observations, while the structure-property relationship between vacancy concentration, distribution, and key detector parameters such as dark current, responsivity, and detectivity remains at the qualitative or empirical correlation stage.

[0005] Lack of effective performance prediction tools: Currently, there is no established computational simulation and theoretical evaluation framework capable of reliably predicting the macroscopic photoelectric response characteristics of devices based on atomic-scale defect structures. While first-principles calculations can reveal the electronic structure of single-point defects, effectively linking them across scales to the transport and photoelectric conversion processes at the device level remains a challenge in theoretical methodology. This makes it difficult to predict and optimize the performance impact of selenium vacancies with specific concentrations and distributions before device fabrication.

[0006] Defect engineering lacks theoretical guidance: Due to the absence of the aforementioned evaluation methods, current defect engineering practices, such as introducing or suppressing selenium vacancies through post-growth processing, elemental doping, and stoichiometric control, largely rely on trial and error or process experience rather than targeted design based on clear theoretical guidance. This lack of direction not only increases R&D costs and time but also limits the possibility of achieving breakthroughs in detector performance limits through precise control of defect states.

[0007] Therefore, providing a theoretical prediction method that can quantitatively assess the impact of selenium vacancies on the performance of infrared detectors, and using this method to guide the active and precise control of defects, is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0008] The purpose of this invention is to provide a method for predicting the infrared nonlinear optical response of Se vacancies in few-layer PtSe2, addressing the problems in the prior art.

[0009] Therefore, the above-mentioned objectives of the present invention are achieved through the following technical solutions: A method for predicting the infrared nonlinear optical response of Se vacancies in few-layer PtSe2 includes the following steps: S1, construct a few-layer PtSe2 model and perform in-plane cell expansion; S2, introduces Se vacancies into the expanded cell model; S3 performs structural relaxation on structures containing Se vacancies until atomic forces and energy converge; S4, electronic band structure of the relaxed structure calculated based on density functional theory; S5. Construct the maximally localized Wannier function and fit the electronic band structure obtained in step S4. S6, Calculate the in-plane nonlinear displacement current component of few-layer PtSe2 in the infrared band; S7. Analyze the changes of the nonlinear displacement current component obtained in step S6 in the infrared band and predict the influence of Se vacancies on infrared nonlinear optical properties.

[0010] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions: As a preferred technical solution of the present invention: In step S1, the few-layer PtSe2 has a 2-layer structure and an in-plane expanded cell of 3×3×1 supercell. The few-layer PtSe2 model is constructed based on the hexagonal crystal system.

[0011] As a preferred technical solution of the present invention: step S2 includes: introducing a Se vacancy by removing a Se atom, wherein the vacancy location is preferably located on the surface of the thin film, including the Se atom of the top or bottom layer.

[0012] As a preferred technical solution of the present invention: In step S3, the structural relaxation is calculated using density functional theory based on the generalized gradient approximation. The plane wave cutoff energy is set to 350 eV based on the generalized gradient approximation PBE functional in density functional theory; the k-point sampling uses the Monkhorst-Pack scheme, and the k-point spacing is set to 0.02 Å. -1 The convergence criterion for structural relaxation is that the Hermann-Feynman force on each atom is less than 5 × 10⁻⁶. -3eV / Å, the energy convergence value of the self-consistent field is set to 10 eV / Å. -5 eV.

[0013] As a preferred technical solution of the present invention: step S4 includes: electronic band structure calculation, using the same exchange-correlation functional and plane wave cutoff energy as step S3; the k-point path is set along the high symmetry point GAMMA-MK-GAMMA to cover the critical path of the Brillouin zone and accurately describe the electronic properties of PtSe2.

[0014] As a preferred technical solution of the present invention: In step S5, when constructing the maximally localized Wannier function, the p-value of the Se atom is selected. z orbitals and dz of Pt atoms 2 The orbit is used as a projection orbit, with a de-entanglement window and a freeze window set, centered on the Fermi level.

[0015] As a preferred embodiment of the present invention, step S6 includes: When calculating the nonlinear displacement current, input the maximally localized Wannier function obtained in step S5; set the infrared band range to 2-20 μm, and calculate the in-plane nonlinear displacement current components; the nonlinear displacement current calculated by Wannier90 is the second-order tensor σ. abc , where a, b, and c represent tensor components, corresponding to the current direction and the light polarization direction; the calculation is for linearly polarized light conditions, when b=c it means that the incident light is linearly polarized light and the polarization direction is limited to in-plane.

[0016] As a preferred embodiment of the present invention, step S7 includes: By comparing current data with and without Se vacancies, the influence of Se vacancies on infrared nonlinear optical properties was analyzed.

[0017] Compared with existing technologies, the method for predicting the infrared nonlinear optical response of Se vacancies in few-layer PtSe2 of the present invention has the following advantages: The present invention constructs a few-layer PtSe2 supercell model containing Se vacancies, and uses first-principles calculations based on density functional theory to solve for structural relaxation and accurate electronic structure. This computationally addresses the uncertainties, sample damage, and high costs associated with experimental preparation, solving the problems of strong experimental dependence and long cycles. It achieves high-precision, low-cost computation to replace experiments, ensuring the accuracy of atomic configuration and electronic state information. Utilizing the maximally localized Wannier function (MLWF) method, the complex electronic band structure obtained from DFT is transformed into a highly accurate and computationally efficient tight-bound Hamiltonian, solving the problem of lack of prior guidance and reliance on trial and error in defect engineering design. This achieves a seamless bridge from first-principles calculations to model computation. Based on the Wannier tight-bound model, using nonlinear response theory, the nonlinear optical response coefficients of the material in the infrared band are directly calculated without any fitting parameters, providing directly usable device design parameters.

[0018] This invention has atomic-level spatial resolution, which can clearly reveal how Se vacancies, as point defects, locally change the electronic density of states and band structure, and ultimately quantitatively affect macroscopic nonlinear optical coefficients. It provides the atomic-scale insight and prediction capability to guide "atomic-level defect engineering".

[0019] This invention combines the accuracy of DFT with the efficiency of tight-binding models, significantly improving computational efficiency while ensuring prediction accuracy. This makes it possible to systematically scan the nonlinear optical properties of large supercells (simulating low defect concentration) and establishes an efficient and reliable multi-scale prediction process.

[0020] The final output of this invention is a nonlinear optical response spectrum (such as the change of displacement current with wavelength) that can be directly correlated with the performance of infrared photodetectors. By comparing the response spectra with and without defects, it can be clearly determined whether Se vacancies "enhance" or "suppress" the response in a specific wavelength band, as well as the peak shift (redshift / blueshift) of the response. This provides directly usable device design parameters, thus providing a quantitative and reliable theoretical basis and design roadmap for optimizing key indicators such as detector sensitivity and spectral selectivity by controlling defect concentration.

[0021] This invention achieves prediction of the infrared nonlinear optical properties of materials solely through calculation, which is low-cost and highly accurate, avoids the uncertainties of experimental preparation, provides a theoretical reference for the subsequent development of related infrared photodetectors, and is of great significance for promoting the application of two-dimensional materials in the field of infrared optoelectronics. Attached Figure Description

[0022] Figure 1This is a flowchart of a method for predicting the infrared nonlinear optical response of Se vacancies in few-layer PtSe2 according to the present invention; Figure 2 This is a schematic diagram of the atomic structure of few-layer PtSe2; Figure 3 Calculate the fitted band plot for the Wannier function and DFT; Figure 4 The curves show the variation of the nonlinear displacement current tensor components in the infrared band (2-20μm). Detailed Implementation

[0023] The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

[0024] To address the challenge of accurately predicting the infrared nonlinear optical response of Se vacancies in few-layer PtSe2 in existing technologies, this invention provides a prediction method based on first-principles calculations. This method, through a systematic computational process, achieves high-precision quantitative prediction of the influence of Se vacancies, providing theoretical guidance for the application of few-layer PtSe2 in infrared photodetectors.

[0025] A method for predicting the infrared nonlinear optical response of Se vacancies in few-layer PtSe2 includes the following steps: S1: Construct a few-layer PtSe2 model and perform in-plane cell expansion; S2: Introduce Se vacancies into the expanded cell model; S3: Perform structural relaxation on the structure containing Se vacancies until atomic forces and energy converge; S4: Electronic band structure of the relaxed structure calculated based on density functional theory; S5: Construct the maximally localized Wannier function and fit the electronic band structure obtained in step S4; S6: Calculate the in-plane nonlinear displacement current components of few-layer PtSe2 in the infrared band using Wannier90 software; S7: Analyze the changes of the nonlinear displacement current component obtained in step S6 in the infrared band and predict the influence of Se vacancies on infrared nonlinear optical properties.

[0026] Step S1 includes: The few-layer PtSe2 has a two-layer structure with an in-plane expanded cell of 3×3×1 supercell; the few-layer PtSe2 model is based on a hexagonal crystal system, and the lattice constant is based on experimental or optimized values.

[0027] Step S2 includes: Se vacancies are introduced by removing a Se atom, with the vacancy location preferably located on the surface of the thin film (Se atoms in the top or bottom layer) to simulate a real defect environment.

[0028] Step S3 includes: Structural relaxation was performed using VASP software, based on the generalized gradient approximation of the PBE functional in density functional theory; the plane wave cutoff energy was set to 350 eV; k-point sampling employed the Monkhorst-Pack scheme, with a k-point spacing of 0.02 Å. -1 The convergence criterion for structural relaxation is that the Hermann-Feynman force on each atom is less than 5 × 10⁻⁶. -3 eV / Å, the energy convergence value of the self-consistent field is set to 10 eV / Å. -5 eV.

[0029] S4 includes: The electronic band structure calculation was performed using VASP software, employing the same exchange-correlation functional and plane-wave cutoff energy as in step S3; the k-point path was set along the high-symmetry point GAMMA-MK-GAMMA to cover the critical path in the Brillouin zone and accurately describe the electronic properties of PtSe2.

[0030] S5 includes: The maximally localized Wannier function was constructed using the Wannier90 software, selecting the p-value of the Se atom. z orbitals and dz of Pt atoms 2 The orbital is used as the projection orbital; the unentanglement window and the freeze window are set with the Fermi level as the center; the constructed Wannier tight-bound Hamiltonian fits well with the energy band calculated by density functional theory near the Fermi level, indicating that it is sufficient to reflect the electronic structure information.

[0031] S6 includes: The nonlinear displacement current calculation is based on Wannier90 software. The maximally localized Wannier function obtained in step S5 is input; the infrared band range is set to 2-20 μm (mid-infrared region), and the in-plane nonlinear displacement current components are calculated; the nonlinear displacement current calculated by Wannier90 is a second-order tensor σ. abc , where a, b, and c represent tensor components, corresponding to the current direction and the light polarization direction; the calculation is for linearly polarized light conditions, when b=c it means that the incident light is linearly polarized light and the polarization direction is limited to in-plane.

[0032] S7 includes: The variation trend of nonlinear displacement current components, such as current enhancement, redshift, or peak position shift, is analyzed. By comparing the current data of structures with and without Se vacancies, the influence of Se vacancies on infrared nonlinear optical properties is analyzed, and theoretical parameters are provided for the design of infrared photodetectors.

[0033] This invention presents a method for predicting the infrared nonlinear optical response of Se vacancies in few-layer PtSe2. By combining first-principles calculations based on density functional theory and analysis using the maximally localized Wannier function, this method achieves high-precision prediction of the impact of Se vacancies on the infrared nonlinear optical properties. The evaluation can be completed solely through computation, avoiding the uncertainties and high costs of experimental preparation. It offers advantages such as atomic-scale precision and high computational efficiency, providing a reliable theoretical basis for defect engineering optimization of few-layer PtSe2 in infrared photodetectors.

[0034] Example 1 This invention provides a method for predicting the infrared nonlinear optical response of Se vacancies in few-layer PtSe2. Based on density functional theory calculations, a PBE functional with a generalized gradient approximation is selected as the exchange-correlation functional. Structural optimization and electronic band structure calculations are performed using VASP software, and a maximally localized Wannier function is constructed using Wannier90 software to simplify the solution for the localized Hamiltonian of the material. This simplifies the calculation of the nonlinear displacement current, thereby predicting the influence of Se vacancies. The flowchart is shown below. Figure 1 The flowchart shown below illustrates a method for predicting the infrared nonlinear optical response of Se vacancies in few-layer PtSe2 according to the present invention, demonstrating the complete sequence of steps from model building to result analysis.

[0035] Step S1: Construct a few-layer PtSe2 model and perform in-plane cell expansion.

[0036] In an optional embodiment, S1 specifically includes: a hexagonal crystal system based on PtSe2, space group P-3m1; lattice parameters, including lattice constants a, b, c and included angles α, β, γ, determined according to experimental data or theoretical calculations; a two-layer thin film model established; and after defining the structure using a VASP POSCAR file, the cell is expanded in multiples of 3×3×1, resulting in a total of 54 atoms. The model construction result is as follows: Figure 2 The diagram shows the atomic structure of few-layer PtSe2, including the complete structure and the model after introducing Se vacancies. The complete structure is a regular arrangement of atoms, while the Se vacancies are achieved by removing a surface Se atom.

[0037] S2: Introduce Se vacancies into the expanded cell model.

[0038] In an optional embodiment, step S2 specifically includes: removing a Se atom by editing the VASP POSCAR file to introduce a vacancy, preferably located on the film surface (Se atoms in the top or bottom layer), to simulate an actual defect environment and determine a suitable vacancy concentration (1 vacancy / 18 Se sites). After introducing the vacancy, the structural symmetry decreases, and the structure file needs to be saved again for subsequent calculations.

[0039] S3: Perform structural relaxation on structures containing Se vacancies until atomic forces and energy converge.

[0040] In an optional embodiment, S3 specifically includes: performing relaxation calculations using VASP software, with the following parameter settings: the exchange-correlated functional is GGA-PBE, the plane wave cutoff energy is set to 350 eV, and the k-point sampling adopts the Monkhorst-Pack scheme (k-point spacing 0.02 Å). -1 (corresponding to a grid of approximately 5×5×1 for k-points), the convergence criterion is that the Herman-Feynman force on each atom is less than 5×10⁻⁶. -3 eV / Å, the energy convergence value of the self-consistent field is set to 10 eV / Å. -5 eV. The optimization algorithm uses the conjugate gradient method (IBRION=2). The relaxation process usually requires 50-100 iterations. The energy converges to a stable value, and the atomic forces are all below the threshold, indicating that the structure has reached a stable state.

[0041] S4: Electronic band structure of the relaxed structure calculated based on density functional theory.

[0042] In an optional embodiment, S4 specifically includes: performing self-consistent calculations using VASP based on the relaxed structure, with parameters consistent with S3, but setting the k-point path along the high-symmetry direction GAMMA-MK-GAMMA to cover the critical path in the Brillouin zone. The band structure calculation results can show changes in the electronic structure near the Fermi level, such as Se vacancy-induced defect states or band shifts.

[0043] S5: Construct the maximally localized Wannier function to fit the electronic band structure obtained in step S4.

[0044] In an optional embodiment, S5 specifically includes: using Wannier90 software to select the p-type of the Se atom. z orbitals and dz of Pt atoms 2 The orbital was used as the projection orbital, and the upper and lower limits of the deentanglement window energy were set to 0.1 eV and -4.26 eV, respectively, while the upper and lower limits of the freeze window energy were set to 0.1 eV and -3.8 eV, respectively, to optimize the localization. The constructed Wannier tight-bound Hamiltonian and the energy band calculated by DFT fit well near the Fermi level, indicating that the Wannier Hamiltonian reflects the electronic structure information near the Fermi surface very well. Figure 3 As shown, this illustrates the agreement near the Fermi level.

[0045] S6: Calculate the in-plane nonlinear displacement current components of few-layer PtSe2 in the infrared band using Wannier90 software.

[0046] In an optional embodiment, S6 specifically includes: calculating the displacement current tensor σ using Wannier90 software based on the Wannier function. abc Where a, b, and c represent tensor components (corresponding to the in-plane x and y directions). The calculation is performed for the infrared band 2-20 μm (mid-infrared region) with linear polarization conditions (b=c, polarization direction limited to in-plane). The calculation results are as follows: Figure 4 As shown, σ is displayed. xxx σ yxx σ yyy σ xyy The variation of nonlinear displacement current components with wavelength in the infrared region.

[0047] S7: Analyze the variation of the nonlinear displacement current component obtained in S6 in the infrared band and predict the influence of Se vacancies on infrared nonlinear optical properties.

[0048] In an optional embodiment, S7 specifically includes: comparing nonlinear displacement current data of structures with and without Se vacancies, such as... Figure 4 The figure shows the variation curves of the nonlinear displacement current tensor components in the infrared band (2-20 μm), revealing the differences in current response induced by Se vacancies. Without Se vacancies, the nonlinear displacement current is almost zero in the 2-20 μm band (all current component values ​​are close to 0), while with Se vacancies, a very obvious nonlinear displacement current peak appears at the 5-7 μm wavelength, such as σ. yyy The component values ​​increased significantly. This result indicates that the introduction of Se vacancies induces a nonlinear optical response, while the response is almost negligible when there are no vacancies. This provides a theoretical reference for related infrared photodetectors designed based on PtSe2.

[0049] Compared with existing technologies, the method for predicting the infrared nonlinear optical response of Se vacancies in few-layer PtSe2 provided by this invention has the following outstanding advantages: 1. A highly efficient and accurate evaluation paradigm driven by computation has been realized; This invention performs the evaluation entirely at the theoretical calculation level, fundamentally avoiding the inherent uncertainties in material preparation, sample damage, and high time and financial costs of traditional experimental methods. By constructing accurate atomic models and performing first-principles calculations, the optical properties of specific defect configurations can be evaluated in a few days or even less, shortening the R&D cycle from months / years of "experimental trial and error" to days / weeks of "computational prediction," realizing a new "computation-first" R&D model with high precision and low cost.

[0050] 2. A multi-scale prediction path for "atomic defects-macroscopic responses" has been established: This invention creatively constructs a multi-scale computational framework of "first-principles calculation (DFT) → maximum localized Wannier function (MLWF) → nonlinear response theory".

[0051] Atomic-scale precision: Atomic-level spatial resolution is ensured through DFT, which can accurately reveal the microscopic effects of Se vacancies on local electronic density of states and band structure.

[0052] Efficient model conversion: Using the MLWF method, the accurate results of DFT are converted into computationally efficient tight-bound Hamiltonians, realizing a seamless and high-fidelity bridge from microscopic electronic structures to mesoscopic physical models.

[0053] Direct calculation of macroscopic properties: Based on this model, the nonlinear optical response coefficients (such as displacement current tensor) of materials in the infrared band can be directly calculated without any empirical fitting parameters. For the first time, quantitative and direct prediction of macroscopic nonlinear optical properties from single atomic defect structures has been realized.

[0054] 3. Provides quantitative theoretical tools to directly guide device design: The final output of this method is a nonlinear optical response spectrum (such as the displacement current versus wavelength curve) that can be directly correlated with the performance indicators of the infrared photodetector. By systematically comparing the response spectra of structures containing Se vacancies with those of intact structures, it is possible to quantitatively determine: Do Se vacancies induce an "enhancement" or "suppression" of the nonlinear response in a specific infrared band? The precise location of the response peak (whether a redshift / blueshift occurs) and its intensity.

[0055] These quantitative results provide clear design parameters and optimization directions for defect engineering of infrared photodetectors (e.g., how to optimize the concentration of Se vacancies in order to pursue ultra-high sensitivity in a specific band), thereby elevating device design from "experience-based trial and error" to "precise design guided by theory".

[0056] 4. It provides a general methodological example for the optical study of defects in two-dimensional materials: The multi-scale computational framework established in this invention is not only applicable to Se vacancies in few-layer PtSe2, but its core methodology of "DFT+MLWF+nonlinear response theory" has the potential to be extended to other two-dimensional transition metal chalcogenides and other types of point defects, providing a powerful and universal theoretical tool for the study of defect properties and device design in the entire field of two-dimensional material optoelectronics.

[0057] The above specific embodiments are used to explain and illustrate the present invention, and are only preferred embodiments of the present invention, not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A method for predicting the infrared nonlinear optical response of Se vacancies in few-layer PtSe2, characterized in that, Includes the following steps: S1, construct a few-layer PtSe2 model and perform in-plane cell expansion; S2, introduces Se vacancies into the expanded cell model; S3 performs structural relaxation on structures containing Se vacancies until atomic forces and energy converge; S4, electronic band structure of the relaxed structure calculated based on density functional theory; S5. Construct the maximally localized Wannier function and fit the electronic band structure obtained in step S4. S6, Calculate the in-plane nonlinear displacement current component of few-layer PtSe2 in the infrared band; S7. Analyze the changes of the nonlinear displacement current component obtained in step S6 in the infrared band and predict the influence of Se vacancies on infrared nonlinear optical properties.

2. The method for predicting the infrared nonlinear optical response of Se vacancies in few-layer PtSe2 according to claim 1, characterized in that, In step S1, the few-layer PtSe2 has a 2-layer structure and an in-plane expanded cell of 3×3×1 supercell. The few-layer PtSe2 model is constructed based on the hexagonal crystal system.

3. The method for predicting the infrared nonlinear optical response of Se vacancies in few-layer PtSe2 according to claim 1, characterized in that, Step S2 includes: introducing a Se vacancy by removing a Se atom, preferably located on the surface of the thin film, including Se atoms in the top or bottom layer.

4. The method for predicting the infrared nonlinear optical response of Se vacancies in few-layer PtSe2 according to claim 1, characterized in that, In step S3, the structural relaxation is calculated using density functional theory based on the generalized gradient approximation (PBE). The plane wave cutoff energy is set to 350 eV based on the PBE. The k-point sampling uses the Monkhorst-Pack scheme, with a k-point spacing of 0.02 Å. -1 The convergence criterion for structural relaxation is that the Hermann-Feynman force on each atom is less than 5 × 10⁻⁶. -3 eV / Å, the energy convergence value of the self-consistent field is set to 10 eV / Å. -5 eV.

5. The method for predicting the infrared nonlinear optical response of Se vacancies in few-layer PtSe2 according to claim 1, characterized in that, Step S4 includes: electronic band structure calculation, using the same exchange-correlation functional and plane wave cutoff energy as in step S3; setting the k-point path along the high-symmetry point GAMMA-MK-GAMMA to cover the critical path of the Brillouin zone and accurately describe the electronic properties of PtSe2.

6. The method for predicting the infrared nonlinear optical response of Se vacancies in few-layer PtSe2 according to claim 1, characterized in that, In step S5, when constructing the maximally localized Wannier function, the p-value of the Se atom is selected. z orbitals and dz of Pt atoms 2 The orbit is used as a projection orbit, with a de-entanglement window and a freeze window set, centered on the Fermi level.

7. The method for predicting the infrared nonlinear optical response of Se vacancies in few-layer PtSe2 according to claim 1, characterized in that, Step S6 includes: When calculating the nonlinear displacement current, input the maximally localized Wannier function obtained in step S5; set the infrared band range to 2-20 μm, and calculate the in-plane nonlinear displacement current components; the nonlinear displacement current calculated by Wannier90 is the second-order tensor σ. abc , where a, b, and c represent tensor components, corresponding to the current direction and the light polarization direction; the calculation is for linearly polarized light conditions, when b=c it means that the incident light is linearly polarized light and the polarization direction is limited to in-plane.

8. The method for predicting the infrared nonlinear optical response of Se vacancies in few-layer PtSe2 according to claim 1, characterized in that, Step S7 includes: By comparing current data with and without Se vacancies, the influence of Se vacancies on infrared nonlinear optical properties was analyzed.

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