XNbBr4O type compound as well as design and performance prediction method and application thereof

Abstract

The invention discloses an XNbBr4O type compound as well as a design and performance prediction method and application thereof, and belongs to the technical field of transition metal doped niobium oxybromide. Wherein X in the XNbBr4O type compound is vanadium, chromium or cobalt, and the compound has magnetic sequence or ferroelectric distortion regulated and controlled by X element doping. The XNbBr4O type compound disclosed by the invention provides a theoretical basis for designing a novel multiferroic photoelectric device, provides an effective way for rapidly screening a high-performance photoelectric material, and has important scientific significance and application value for guiding subsequent experimental synthesis and device design.

Description

Technical Field

[0001] This invention relates to the field of transition metal doped niobium bromide technology, and particularly to XNbBr4O compounds, their design and performance prediction methods, and applications. Background Technology

[0002] With the rapid development of optoelectronic devices towards high efficiency, miniaturization, and multifunctionality, traditional semiconductors such as Si and GaAs, limited by fixed band gaps and low spin polarization, are finding it difficult to meet the new demands for wide-band visible-infrared response and spin manipulation. In recent years, researchers have attempted to modulate the optoelectronic properties of transition metal oxides through doping, straining, and heterojunction engineering. However, limitations in lattice matching and process complexity have resulted in long experimental trial-and-error cycles, high costs, and limited tuning amplitude. Therefore, there is an urgent need to find novel material systems with intrinsically tunable optoelectronic properties and develop theoretical design methods that can predict their performance without experiments, in order to shorten material development cycles and reduce R&D costs.

[0003] Multiferroic materials, possessing both ferroelectric and ferromagnetic order, can achieve degree-of-freedom coupling of charge, spin, and lattice within a single phase, providing an additional dimension for the performance tuning of optoelectronic devices. Ferroelectricity can introduce a built-in electric field through ion displacement, promoting the separation of photogenerated carriers; ferromagnetism provides spin-polarized transport channels, potentially improving device response speed and reducing power consumption. However, reported multiferroic oxides (such as BiFeO3 and TbMnO3) generally suffer from excessively large band gaps (greater than 2.5 eV) or weak ferromagnetic moments (less than 0.1 μB / fu), severely limiting their application in visible-infrared optoelectronic devices. Therefore, the search for novel multiferroic candidate materials with narrow band gaps, high polarization intensity, and high magnetic moments has become a current research hotspot.

[0004] Niobium-based halide oxides (NbBr₂O) have recently been theoretically predicted as layered polar semiconductors. Their flexible lattice and diverse coordination environments provide an ideal platform for transition metal doping. However, systematic research is still lacking on whether ferromagnetism can stably exist within them and the mechanism by which it affects photoelectric properties. Traditional experimental methods are insufficient for in-situ analysis of the correlation between doping-induced microscopic electronic structure and macroscopic photoelectric response. Summary of the Invention

[0005] Purpose of the invention: To address the above problems, the purpose of this invention is to provide XNbBr4O type compounds, their design and performance prediction methods and applications, and to directionally design XNbBr4O type candidate materials with narrow band gap, high carrier mobility, strong spin polarization and wide-band light absorption, so as to provide theoretical basis and material solutions for the experimental synthesis and preparation of high-performance photodetectors, spin valves and infrared photocatalytic devices.

[0006] Technical solution: In a first aspect, the present invention provides an XNbBr4O type compound with the general chemical formula XNbBr4O, wherein X is vanadium, chromium or cobalt, and the compound has magnetic order or ferroelectric distortion regulated by doping with element X.

[0007] Furthermore, when X is chromium or cobalt, the compound exhibits ferroelectric distortion, with calculated band gap values ​​ranging from 1.6 eV to 2.0 eV.

[0008] Furthermore, when X is vanadium, the compound exhibits a ferromagnetic order and macroscopically displays magnetism.

[0009] Secondly, this invention provides a method for designing and predicting the performance of XNbBr4O type compounds, comprising the following steps:

[0010] S1: Based on the general chemical formula XNbBr4O, a supercell crystal model containing the doping element X is constructed;

[0011] S2: Using density functional theory combined with Hubbard correction, the supercell crystal model was structurally optimized and its energy was calculated to determine its stable magnetic ground state.

[0012] S3: Based on the optimized magnetic order structure, calculate the electronic band structure, effective carrier mass and optical absorption coefficient of compound XNbBr4O;

[0013] S4: Based on the calculation results of step S3, evaluate the photoelectric properties of the compound in the visible to infrared bands for different X elements.

[0014] Furthermore, in step S2, the lattice parameters and atomic coordinates of the XNbBr4O type compound are optimized using the conjugate gradient algorithm.

[0015] Thirdly, the present invention provides a visible-infrared optoelectronic device or a spin optoelectronic device of an XNbBr4O type compound.

[0016] Beneficial effects: Compared with the prior art, the significant advantages of this invention are:

[0017] 1. This invention reveals the regulation law of magnetic order on the photoelectric properties of XNbBr4O compounds through first-principles calculations. It can obtain candidate materials with narrow band gap, high spin polarization and strong infrared absorption without experimentation, which significantly shortens the research and development cycle, reduces trial and error costs, and provides a theoretical basis and material scheme for the direct synthesis of high-performance optoelectronic devices such as infrared detectors, spin valves and semi-metallic electrodes.

[0018] 2. The layered Pmm2 structure in the XNbBr4O compound naturally shields the interlayer coupling, which facilitates the mechanical exfoliation to prepare single-layer or few-layer flexible devices;

[0019] 3. All elements in the XNbBr4O compound are transition metals and halogens that are highly abundant in the Earth's crust, avoiding precious metals and toxic As / Pb, resulting in low synthesis cost and environmental friendliness.

[0020] 4. The supercell model of XNbBr4O compounds is directly compatible with existing mainstream software such as VASP and Quantum ESPRESSO, which significantly reduces the threshold for integrated research and development of materials and devices, and provides a theoretical basis and material library that can be immediately implemented in the fields of infrared detection, spintronics, photocatalysis and flexible electronics.

[0021] 5. This invention optimizes the structure of XNbBr4O type compounds using high-precision first-principles DFT+U and the conjugate gradient method. Point density pair The supercell performs high-throughput calculations, calculating four initial configurations—ferromagnetic, A / C / G type antiferromagnetic—in one go, quickly determining the magnetic ground state, and realizing the entire process of calculation, discrimination, and screening, which greatly reduces the trial-and-error cost compared to traditional experimental methods.

[0022] 6. XNbBr4O compounds, through V-doping systems, achieve high spin polarization and a macroscopic magnetic moment ≥2 μB / fu, providing a half-metal injection source for low-power spin valves. Through Cr / Co doping systems... It exhibits both ferroelectric polarization and strong visible-infrared absorption within a narrow bandgap, with an absorption coefficient greater than [missing value]. The built-in electric field promotes the separation of photogenerated carriers, which can theoretically improve photoelectric conversion efficiency. Attached Figure Description

[0023] Figure 1 Here is the structural diagram of XNbBr4O;

[0024] Figure 2 The band structure diagram of CrNbBr4O is shown below.

[0025] Figure 3 The band structure diagram of CoNbBr4O;

[0026] Figure 4 The graph shows the light absorption coefficients of XNbBr4O with different doping levels. Detailed Implementation

[0027] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and not intended to limit the scope of the invention. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the embodiments of the present invention, and not all structures.

[0028] In the following description, specific details such as target system architecture and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of this application with unnecessary detail.

[0029] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0030] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0031] Furthermore, in the description of this application and the appended claims, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0032] References to "one embodiment" or "some embodiments" in this specification mean that one or more embodiments of this application include the target features, structures, or characteristics described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized.

[0033] The XNbBr4O type compound described in this embodiment has the general chemical formula XNbBr4O, where X is vanadium, chromium or cobalt, and the compound has magnetic order or ferroelectric distortion regulated by doping with element X.

[0034] Based on the two-dimensional material NbBr2O, ferromagnetic order is introduced by doping with the transition metal X, thereby modulating the light absorption, carrier migration and photoresponse properties of XNbBr4O, making it a candidate optoelectronic material with narrow bandgap, high carrier mobility, strong spin polarization and wide-band light absorption.

[0035] Furthermore, when X is chromium or cobalt, the compound exhibits ferroelectric distortion, with calculated band gap values ​​ranging from 1.6 eV to 2.0 eV.

[0036] Furthermore, when X is vanadium, the compound exhibits ferromagnetic order and high spin polarizability.

[0037] Figure 1 The diagram shows the side view, top view, and expanded cell structure of a single-layer XNbBr4O crystal. XNbBr4O has a Pmm2 space group structure and the ferroelectric polarization direction is the a direction.

[0038] Figure 2 The image shows the band structure of CrNbBr4O. Figure 3 The image shows the band structure of CoNbBr4O. The red solid lines represent spin-down bands, and the blue solid lines represent spin-up bands. The band structure diagram shows that the band gaps of both CrNbBr4O and CoNbBr4O are within the range of... The results further demonstrate that XNbBr4O can absorb visible light very well, and can serve as a candidate material for XNbBr4O with narrow bandgap, high carrier mobility, strong spin polarization and wide-band light absorption, providing a theoretical basis and material scheme for the experimental synthesis and preparation of high-performance photodetectors, spin valves and infrared photocatalytic devices.

[0039] In other embodiments of the present invention, a method for designing and predicting the performance of XNbBr4O type compounds is also provided, comprising the following steps:

[0040] S1: Based on the chemical formula XNbBr4O, construct a supercell crystal model containing dopant element X.

[0041] In one example, using the VASP software package, the experimental lattice constant of the parent NbBr4O is extracted from the database to construct a 28-atom array. The supercell ensures that various magnetic orders can be set for subsequent operations, and the vacuum layer is set to... Introducing X (at the Nb site) Single-atom doping was performed, and an undoped control model was established. For each system, ferroelectric distortion (Nb displacement along the z-axis of 0–20 pm) and magnetic order (ferromagnetic FM, A-type, C-type and G-type antiferromagnetic AFM) were considered, resulting in four initial configurations and generating an initial crystal structure POSCAR file.

[0042] S2: Using density functional theory combined with Hubbard correction, the supercell crystal model is structurally optimized and its energy is calculated to determine its stable magnetic ground state.

[0043] Furthermore, in S2, the conjugate gradient algorithm is used to optimize the lattice parameters and atomic coordinates of the XNbBr4O type compound.

[0044] Density functional theory (PBE) combined with Hubbard modified (U) functionals is employed, with U values ​​pre-calibrated using the linear response method: X-3d according to element-wise... Range of values; parameters in INCAR are set to: ISIF=3, IBRION=2, and K-points in the KPOINTS file are set to... Static calculations are performed once the optimized structure meets the convergence criteria. The ISIF parameter controls which degrees of freedom are optimized during the structure optimization process. ISIF = 3 indicates simultaneous optimization of lattice parameters and atomic coordinates, the most commonly used setting, suitable for situations requiring simultaneous adjustment of lattice volume and atomic positions. The IBRION parameter selects the ion relaxation algorithm, i.e., the method for atomic position optimization. IBRION = 2 indicates the use of the Conjugate Gradient (CG) algorithm. The Conjugate Gradient algorithm is an efficient optimization method suitable for most structure optimization problems, especially those requiring fast convergence. It iteratively optimizes atomic positions to minimize the system's energy. The KPOINTS file defines the sampling points (k-points) of the Brillouin zone. The choice of k-points significantly impacts computational accuracy and cost. This indicates that 9, 5, and 1 k-points are set in the three directions of the Brillouin zone, respectively. For two-dimensional materials (such as XNbBr4O), since they have a layered structure in the out-of-plane direction, only 1 k-point is set in the vertical direction (z-direction). More k-points are set in the in-plane directions (x and y directions) to ensure more accurate sampling of the electronic structure of the two-dimensional plane.

[0045] Calculation of Heisenberg exchange constant based on ground state structure ,use Supercell, calculating the total energy of FM and AFM by changing the spin direction. and Substitute into the formula Solve ,in Take the integer of the OUTCAR magnetic moment, if And total magnetic moment If it is ferromagnetically ordered, then it is determined to be ferromagnetically ordered; if If the magnetic moments cancel each other out, then it is determined to be an antiferromagnetic ordered system.

[0046] S3: Based on the optimized magnetic order structure, calculate the electronic band structure, effective carrier mass, and optical absorption coefficient of the compound.

[0047] After the static self-consistent calculation is completed, the INCAR parameters are modified based on the static self-consistency, where ISTART = 1, ICHARG = 11, LORBIT = 11, and LWAVE = FALSE. The PBE method is used to calculate the photoelectric properties, obtain the stable band structure, density of states, and light absorption coefficient, and the Origin plotting tool is used to analyze and plot the data of density of states, band structure, and light absorption coefficient.

[0048] Figure 4 The diagram shows the light absorption coefficients of XNbBr4O under different doping conditions. It can be seen that XNbBr4O exhibits excellent absorption in the near-red and near-violet regions of the visible light spectrum regardless of whether it is doped with any of the transition metals V, Cr, or Co. However, in the infrared and ultraviolet bands, the absorption does not change significantly with different doping transition metals.

[0049] S4: Based on the calculation results of step S3, evaluate the photoelectric properties of the compound in the visible to infrared bands for different X elements.

[0050] This example uses DFT+U calculations to study the effects of doping-introduced ferromagnetic order on band structure, light absorption, and spin polarization. It provides a theoretical basis for designing novel multiferroic optoelectronic devices, offers an effective way to rapidly screen high-performance optoelectronic materials, and has significant scientific and application value for guiding subsequent experimental synthesis and device design.

[0051] This invention also provides a visible-infrared optoelectronic device or a spin optoelectronic device of an XNbBr4O type compound.

Claims

1. An XNbBr4O type compound, characterized in that, Its general chemical formula is XNbBr4O, where X is vanadium, chromium or cobalt, and the compound has magnetic order or ferroelectric distortion regulated by doping with the element X.

2. The XNbBr4O type compound according to claim 1, characterized in that, When X is chromium or cobalt, the compound exhibits ferroelectric distortion, with calculated band gap values ​​ranging from 1.6 eV to 2.0 eV.

3. The XNbBr4O type compound according to claim 1, characterized in that, When X is vanadium, the compound exhibits a ferromagnetic order and macroscopically displays magnetism.

4. A method for designing and predicting the performance of XNbBr4O type compounds as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1: Based on the general chemical formula XNbBr4O, a supercell crystal model containing the doping element X is constructed; S2: Using density functional theory combined with Hubbard correction, the supercell crystal model was structurally optimized and its energy was calculated to determine its stable magnetic ground state. S3: Based on the optimized magnetic order structure, calculate the electronic band structure, effective carrier mass and optical absorption coefficient of compound XNbBr4O; S4: Based on the calculation results of step S3, evaluate the photoelectric properties of different X elements on the compound in the visible to infrared band.

5. The method for designing and predicting the performance of XNbBr4O type compounds according to claim 4, characterized in that, In step S2, the conjugate gradient algorithm is used to optimize the lattice parameters and atomic coordinates of the XNbBr4O type compound.

6. A visible-infrared optoelectronic device or a spin optoelectronic device comprising the XNbBr4O type compound according to any one of claims 1 to 3.

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