Modeling Method and Application of a Two-Dimensional Janus Material

Abstract

The present invention provides a modeling method for two-dimensional Janus materials, including: importing an MX2 unit cell from a material database, replacing the X atoms on one side with Y atoms to obtain an MXY unit cell; converting the MXY unit cell from a hexagonal unit cell to a rectangular unit cell to obtain an MXY rectangular unit cell; expanding the MXY rectangular unit cell, inverting one of the supercells, and then connecting the inverted supercell along the zigzag edge and the armchair edge to respectively form an in-plane heterojunction with a zigzag boundary and an in-plane heterojunction with an armchair boundary; performing structural relaxation on it, and thus completing the modeling of the two-dimensional Janus material. Through this method, the present invention can construct an MXY inverted heterostructure, which is consistent with the characteristics of the out-of-plane asymmetric structure of the material itself, can truly reflect the structure of the two-dimensional Janus material in the suspended state, and can provide a reasonable structural model for the study of two-dimensional Janus materials.

Description

Technical Field

[0001] The present invention relates to the field of analog computing technology, and more particularly, to a method for modeling two-dimensional Janus materials and its applications. Background Art

[0002] In recent years, two-dimensional layered materials have received unprecedented attention due to their special structures and properties, which have had a huge impact on the design of electronic devices. Among them, two-dimensional Janus materials are a type of two-dimensional material with special properties of double-sided functional asymmetry, and these materials have good optical, electrical, mechanical response, nonlinear optical response, and catalytic properties, and can be applied to optoelectronic detectors and solar cell materials. Common two-dimensional Janus materials mainly include binary compounds MX formed by Group IVA and Group VIA elements (where M = Ge, Sn; X = S, Se); binary compounds AB formed by Group VA elements (where A = P, Sb; B = N, As), etc.

[0003] Currently, in the research of two-dimensional Janus materials, due to the limitation of the periodic boundary conditions of two-dimensional materials, the selected two-dimensional Janus material models are all planar structures. Obviously, this planar structure model does not conform to the out-of-plane asymmetric structure characteristics of two-dimensional Janus materials themselves, affecting the accuracy of the simulation research on the structures and properties of two-dimensional Janus materials. Summary of the Invention

[0004] The problem solved by the present invention is how to provide a modeling method that conforms to the out-of-plane asymmetric structure characteristics of two-dimensional Janus materials themselves.

[0005] To solve at least one of the above problems, the present invention provides a method for modeling two-dimensional Janus materials, including the following steps:

[0006] Step S1: Import the MX 2 unit cell from the material database, replace one side of the X atom with a Y atom to form an asymmetric unit cell, where the M atom is an element of Group IVA or VA, the X atom and the Y atom are elements of Group VA or VIA, and the X atom and the Y atom are different, to obtain the MXY unit cell;

[0007] Step S2: Convert the MXY unit cell from a hexagonal unit cell to a rectangular unit cell to obtain the MXY rectangular unit cell;

[0008] Step S3: Expand the MXY rectangular unit cell to obtain two MXY supercells, invert one of the supercells, and then connect the inverted supercell along the zigzag edge and the armchair edge to form an in-plane heterojunction with a zigzag boundary and an in-plane heterojunction with an armchair boundary, respectively;

[0009] Step S4: Perform structural relaxation on the in-plane heterojunction with zigzag boundaries and the in-plane heterojunction with armchair boundaries to obtain the MXY inverted heterostructure, completing the modeling of the two-dimensional Janus material.

[0010] Preferably, the M atom includes one of Mo, Ge, Sn, P, and Sb, the X atom and the Y atom include one of S, Se, Te, N, and As, and the X atom and the Y atom are different.

[0011] Preferably, the M atom is Mo, the X atom is S, and the Y atom is Te.

[0012] Preferably, in step S1, the simulation calculation is performed in the first-principles calculation software VASP. During the calculation, the outer electrons of the M atom, the X atom, and the Y atom are regarded as valence electrons, the projector augmented wave method is used to describe the core-valence interaction, and the Perdew-Burke-Ernzerhof generalized gradient approximation is used for the exchange-correlation function.

[0013] Preferably, the method for modeling the two-dimensional Janus material further includes, after obtaining the MXY unit cell, performing structural relaxation on the MXY unit cell under the condition that the energy cutoff value of the plane wave expansion is 100 eV, using a 10×2×1 grid for calculation, and allowing all atoms to be relaxed until the Hellmann-Feynman force on each atom calculated is less than wherein, the electronic convergence accuracy is set to 1E-5, and the ionic convergence accuracy is set to 1E-2.

[0014] Preferably, during the relaxation process of the MXY unit cell, a vacuum layer of is added in the z direction to avoid the interaction between adjacent heterostructures.

[0015] Preferably, in step S4, all atoms are allowed to be relaxed until the Hellmann-Feynman force on each atom calculated is less than wherein, the electronic convergence accuracy is set to 1E-5, and the ionic convergence accuracy is set to 1E-2, so as to perform structural relaxation on the in-plane heterojunction with zigzag boundaries and the in-plane heterojunction with armchair boundaries.

[0016] The present invention by combining MX 2Replace the X atom on one side of the unit cell with a Y atom to obtain the MXY unit cell, and perform structural relaxation on the MXY unit cell to make its structural parameters consistent with the experimental values. Then, convert the structurally relaxed MXY unit cell from a hexagonal unit cell to a rectangular unit cell, expand the cell and invert it, and perform structural relaxation on the inverted heterojunction to construct the MXY inverted heterostructure. This inverted heterostructure is consistent with the out-of-plane asymmetric structure characteristics of the material itself, can truly reflect the structure of the two-dimensional Janus material in the suspended state, and can provide a reasonable structural model for the study of two-dimensional Janus materials.

[0017] Another object of the present invention is to provide an application of the modeling method for two-dimensional Janus materials, which is the application of the two-dimensional Janus materials constructed by the above-mentioned modeling method for two-dimensional Janus materials in the prediction of their structures and properties.

[0018] Preferably, import the two-dimensional Janus material into the first-principles calculation software VASP, use the generalized gradient approximation calculation, set the energy cut-off value of the plane wave expansion to 400 eV, fix the lattice and use VASPKIT to automatically generate high-symmetry points as K points, and generate a network along the high-symmetry points, where the electronic convergence accuracy is set to 1E-5 and the ionic convergence accuracy is set to 1E-2, and calculate the energy band and density of states of the two-dimensional Janus material.

[0019] By applying the above-mentioned modeling method for two-dimensional Janus materials to the prediction of the structures and properties of two-dimensional Janus materials, various two-dimensional Janus materials can be obtained through computer simulation methods, and the structures of the two-dimensional Janus materials simulated by this method can truly reflect their structures in the suspended state, so that the structures and properties of two-dimensional Janus materials can be accurately predicted, significantly improving the research efficiency and the accuracy of data. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a flowchart of the modeling method for two-dimensional Janus materials in an embodiment of the present invention;

[0021] Figure 2 is a structural diagram of the MoSTe unit cell in an embodiment of the present invention;

[0022] Figure 3 is a structural diagram of the MoSTe rectangular unit cell in an embodiment of the present invention;

[0023] Figure 4 is a structural diagram of the MoSTe inverted heterojunction in an embodiment of the present invention;

[0024] Figure 5 is a schematic diagram of the MoSTe inverted heterostructure in an embodiment of the present invention;

[0025] Figure 6 This is the energy band diagram of the MoSTe inversion heterostructure in the embodiments of the present invention;

[0026] Figure 7 This is the density of states diagram of the MoSTe inversion heterostructure in the embodiments of the present invention. Detailed implementation manners

[0027] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention is provided.

[0028] It should be noted that, without conflict, the features in the embodiments of the present invention can be combined with each other. The meanings of the terms "comprising", "including", "containing", and "having" are non-limiting, that is, other steps and other components that do not affect the result can be added. The above terms cover the terms "consisting of" and "consisting essentially of". Unless otherwise specified, materials, equipment, and reagents are commercially available.

[0029] The embodiments of the present invention provide a modeling method for two-dimensional Janus materials, as Figure 1 shown, including the following steps:

[0030] Step S1: Import the MX 2 unit cell from the material database, and replace one side of the X atoms with Y atoms to form an asymmetric unit cell, where the M atom is an element of Group IVA or VA, the X atom and the Y atom are elements of Group VA or VIA, and the X atom and the Y atom are different, to obtain the MXY unit cell;

[0031] Step S2: Convert the MXY unit cell from a hexagonal unit cell to a rectangular unit cell to obtain the MXY rectangular unit cell;

[0032] Step S3: Expand the MXY rectangular unit cell to obtain two MXY supercells, invert one of the supercells, and then connect the inverted supercell along the zigzag edge and the armchair edge to form an in-plane heterojunction with a zigzag boundary and an in-plane heterojunction with an armchair boundary respectively;

[0033] Step S4: Perform structural relaxation on the in-plane heterojunction with a zigzag boundary and the in-plane heterojunction with an armchair boundary to obtain the MXY inversion heterostructure, and complete the modeling of the two-dimensional Janus material.

[0034] In step S1, import the MX 2A unit cell has one of the X atoms on one side replaced by a Y atom to form an asymmetric unit cell. Here, the M atom is an element of Group IVA or VA, the X atom and the Y atom are elements of Group VA or VIA, and the X atom and the Y atom are different, resulting in an MXY unit cell. The simulation calculation is carried out in the first-principles calculation software VASP. During the calculation, the outermost electrons of the M atom, X atom, and Y atom are regarded as valence electrons, and the projector augmented wave method (PAW) is used to describe the core-valence interaction. The exchange-correlation function adopts the generalized gradient approximation of Perdew-Burke-Ernzerhof (GGA-PBE). Binary compounds composed of Group IVA elements and Group VIA elements, as well as between Group VA elements, are common forms of two-dimensional Janus materials. By using a Y atom to replace one of the X atoms, a two-dimensional Janus material with an asymmetric structure can be formed.

[0035] Specifically, the M atom includes one of Mo, Ge, Sn, P, and Sb, the X atom and the Y atom include one of S, Se, Te, N, and As, and the X atom and the Y atom are different. And M is preferably Mo, the X atom is preferably S, and the Y atom is preferably Te.

[0036] After obtaining the MXY unit cell, perform structural relaxation on it to make it consistent with the experimental value. The method of structural relaxation is: perform structural relaxation on the MXY unit cell under the condition that the energy cutoff value of plane wave expansion is 100 eV, use a 10×2×1 grid for calculation, and all atoms are allowed to be relaxed until the Hellmann-Feynman force on each calculated atom is less than where the electronic convergence accuracy is set to 1E-5, the ionic convergence accuracy is set to 1E-2, and a vacuum layer of is added in the z direction to avoid interaction between adjacent heterostructures.

[0037] In step S2, convert the MXY unit cell from a hexagonal unit cell to a rectangular unit cell to obtain an MXY rectangular unit cell. After converting the MXY unit cell from a hexagonal unit cell to a rectangular unit cell, it is convenient to expand the cell and perform inversion to form a heterostructure.

[0038] In step S3, expand the MXY unit cell to obtain two MXY supercells, invert one of the supercells, and then connect the inverted supercell along the zigzag edge and the armchair edge to form an in-plane heterojunction with a zigzag boundary and an in-plane heterojunction with an armchair boundary respectively. By inverting one of the supercells and connecting the inverted supercell along the zigzag edge and the armchair edge, two heterojunctions can be formed, obtaining the characteristics consistent with the out-of-plane asymmetric structure of the two-dimensional Janus material itself.

[0039] In step S4, structural relaxation is performed on the in-plane heterojunction with zigzag boundaries and the in-plane heterojunction with armchair boundaries. During the structural relaxation process, all atoms are allowed to be relaxed until the Hellmann-Feynman force on each atom calculated is less than where the electronic convergence accuracy is set to 1E-5 and the ionic convergence accuracy is set to 1E-2, so as to perform structural relaxation on the in-plane heterojunction with zigzag boundaries and the in-plane heterojunction with armchair boundaries, obtaining the MXY inverted heterostructure, that is, the modeling of the two-dimensional Janus material is completed.

[0040] By replacing X on one side of the MX 2 unit cell with Y atoms, an MXY unit cell is obtained, and structural relaxation is performed on the MXY unit cell to make its structural parameters consistent with the experimental values. Then, the structurally relaxed MXY unit cell is converted from a hexagonal unit cell to a rectangular unit cell, and the cell is expanded and inverted, and structural relaxation is performed on the inverted heterojunction, thereby constructing an MXY inverted heterostructure. This inverted heterostructure is consistent with the out-of-plane asymmetric structure characteristics of the material itself, can truly reflect the structure of the two-dimensional Janus material in the suspended state, and can provide a reasonable structural model for the study of two-dimensional Janus materials.

[0041] Another embodiment of the present invention provides an application of the modeling method of a two-dimensional Janus material, which is the application of the two-dimensional Janus material constructed by the above-mentioned modeling method of a two-dimensional Janus material in the prediction of its structure and properties.

[0042] Specifically, the two-dimensional Janus material is imported into the first-principles calculation software VASP, and the generalized gradient approximation is used for calculation. The energy cutoff value of the plane wave expansion is set to 400 eV. The VASPKIT is used to automatically generate high-symmetry points as K points while fixing the lattice, and a network is generated along the high-symmetry points. Among them, the electronic convergence accuracy is set to 1E-5 and the ionic convergence accuracy is set to 1E-2 to calculate the energy band and density of states of the two-dimensional Janus material.

[0043] By applying the above-mentioned modeling method of a two-dimensional Janus material to the prediction of the structure and properties of a two-dimensional Janus material, various two-dimensional Janus materials can be obtained through computer simulation methods, and the structure of the two-dimensional Janus material simulated by this method can truly reflect its structure in the suspended state, so as to accurately predict the structure and properties of the two-dimensional Janus material, significantly improving the research efficiency and the accuracy of data.

[0044] The following introduces the modeling method of a two-dimensional Janus material and its application in combination with specific embodiments:

[0045] Embodiment

[0046] 1.1. Import the MoS 2 unit cell from the material database, replace the S atoms on one side with Te atoms to form an asymmetric unit cell, and obtain the MoSTe unit cell. Among them, the simulation calculation is carried out in the first-principles calculation software VASP. During the calculation, the outer electrons of Mo atoms, S atoms, and Te atoms are regarded as valence electrons, and the projector augmented wave method (PAW) is used to describe the core-valence interaction. The generalized gradient approximation of Perdew-Burke-Ernzerhof (GGA-PBE) is adopted for the exchange-correlation function. Then, structural relaxation is performed on the MoSTe unit cell. The energy cutoff value of the plane wave expansion is set to 400 eV, and a 10×2×1 grid is used for the calculation, and all atoms are allowed to relax until the Hellmann-Feynman force on each atom is calculated to be less than The electronic convergence accuracy is set to 1E-5, and the ionic convergence accuracy is set to 1E-2;

[0047] As Figure 2 shown, the structural parameters of the MoSTe unit cell after structural relaxation are The Mo-S bond length is consistent with the experimental value, where a and b are both the unit cell side length parameters of the lattice, and the directions of a and b are as Figure 2 shown.

[0048] 1.2. Convert the MoSTe unit cell from a hexagonal unit cell to a rectangular unit cell to obtain the MoSTe rectangular unit cell;

[0049] Among them, Figure 3 is the structural diagram of the MoSTe rectangular unit cell;

[0050] 1.3. Expand the MoSTe rectangular unit cell to obtain two MoSTe supercells, invert one of the supercells, and then connect the inverted supercell along the zigzag edge and the armchair edge to form an in-plane heterojunction with a zigzag boundary and an in-plane heterojunction with an armchair boundary respectively. Among them, Figure 4 is the structural diagram of the MoSTe inverted heterojunction;

[0051] 1.4. Perform structural relaxation on the in-plane heterojunction with a zigzag boundary and the in-plane heterojunction with an armchair boundary. During the structural relaxation process, all atoms are allowed to relax until the Hellmann-Feynman force on each atom is calculated to be less than Among them, the electronic convergence accuracy is set to 1E-5, and the ionic convergence accuracy is set to 1E-2, to obtain the MoSTe inverted heterostructure after structural relaxation, that is, the modeling of the MoSTe material is completed;

[0052] Among them, Figure 5 is the schematic diagram of the MoSTe inverted heterostructure after structural relaxation, and two parameters are defined to describe it. Among them, And the structure significantly shows a structural bend, with a bending angle of 143.49°, presenting a structure similar to a sine curve; in addition, there is an obvious rearrangement of the atomic structure at the heterojunction boundary. The structure configuration near the boundary is between the 2H and 1T structures, and at the heterojunction interface, the bond lengths change significantly. The lengths of the Mo-Te bonds at other positions are between, while there are and two Mo-Te bonds with significantly different lengths at the two interfaces. At the same time, there are and two types of bond lengths for the Mo-S bonds at non-interface positions, and and two special Mo-S bonds appear at the interface. Therefore, due to the van der Waals force of the structure itself, the ionic bond lengths at the interface change significantly compared with other parts;

[0053] 1.5. Import the MoSTe inverse heterostructure constructed in step 1.4 into the first-principles calculation software VASP. Use the generalized gradient approximation for calculation. Set the energy cutoff value of the plane wave expansion to 400 eV. Fix the lattice and use VASPKIT to automatically generate high-symmetry points as K points, and generate a network along the high-symmetry points. Set the electron convergence accuracy to 1E-5 and the ionic convergence accuracy to 1E-2, and calculate the energy band and density of states of the MoSTe inverse heterostructure;

[0054] As Figure 6 shown, Figure 6 is the energy band diagram of the MoSTe inverse heterostructure. It can be seen from the figure that the maximum value of the conduction band (VBM) and the minimum value of the valence band (CBM) in the MoSTe inverse heterostructure are both at the Γ symmetry point, and the energy band structure is a direct bandgap with a bandgap width of 1.23 eV.

[0055] As Figure 7 shown, Figure 7 is the density of states diagram of the MoSTe inverse heterostructure. It can be seen from the figure that the d orbitals of Mo atoms provide the main contribution near the Fermi level. At the same time, the p orbitals of S atoms and the p orbitals of Te atoms form p-p orbital coupling, providing the remaining contribution near the Fermi level.

[0056] Although the present disclosure is disclosed as above, the protection scope of the present disclosure is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure, and these changes and modifications will all fall within the protection scope of the present invention.

Claims

1. A modeling method for two-dimensional Janus materials, characterized in that, it includes the following steps: Step S1: Import MX from the material database 2 unit cell, replace the X atoms on one side with Y atoms to form an asymmetric unit cell, where the M atom is an element of Group IVA or VA, the X atom and the Y atom are elements of Group VA or VIA, and the X atom and the Y atom are different, to obtain an MXY unit cell; Step S2: Convert the MXY unit cell from a hexagonal unit cell to a rectangular unit cell to obtain an MXY rectangular unit cell; Step S3: Expand the MXY rectangular unit cell to obtain two MXY supercells, invert one of the supercells, and then connect the inverted supercell along the zigzag edge and the armchair edge to form an in-plane heterojunction with a zigzag boundary and an in-plane heterojunction with an armchair boundary respectively; Step S4: Perform structural relaxation on the in-plane heterojunction with a zigzag boundary and the in-plane heterojunction with an armchair boundary to obtain an MXY inverted heterostructure, completing the modeling of the two-dimensional Janus material.

2. The modeling method for two-dimensional Janus materials according to claim 1, characterized in that, the M atom includes one of Mo, Ge, Sn, P, and Sb, the X atom and the Y atom include one of S, Se, Te, N, and As, and the X atom and the Y atom are different.

3. The modeling method for two-dimensional Janus materials according to claim 2, characterized in that, the M atom is Mo, the X atom is S, and the Y atom is Te.

4. The modeling method for two-dimensional Janus materials according to claim 1, characterized in that, in step S1, the simulation calculation is carried out in the first-principles calculation software VASP. During the calculation, the outer electrons of the M atom, the X atom, and the Y atom are regarded as valence electrons, the projector augmented wave method is used to describe the core-valence interaction, and the Perdew-Burke-Ernzerhof generalized gradient approximation is adopted for the exchange-correlation function.

5. The modeling method for two-dimensional Janus materials according to claim 3, characterized in that, It also includes that after obtaining the MXY unit cell, performing structural relaxation on the MXY unit cell under the condition that the energy cut-off value of plane wave expansion is 100 eV, calculating using a 10×2×1 grid, and allowing all atoms to be relaxed until the Hellmann-Feynman force on each atom calculated is less than wherein the electronic convergence accuracy is set to 1E-5 and the ionic convergence accuracy is set to 1E-2.

6. The modeling method for two-dimensional Janus materials according to claim 5, characterized in that, During the relaxation process of the MXY unit cell, a vacuum layer of is added in the z direction to avoid the interaction between adjacent heterostructures.

7. The modeling method for two-dimensional Janus materials according to claim 3, characterized in that, In the step S4, all atoms are allowed to be relaxed until the Hellmann-Feynman force on each atom calculated is less than wherein, The electronic convergence accuracy is set to 1E-5, and the ionic convergence accuracy is set to 1E-2, so as to perform structural relaxation on the in-plane heterojunction with a zigzag boundary and the in-plane heterojunction with an armchair boundary.

8. An application of a modeling method for two-dimensional Janus materials, characterized in that, it is an application of the two-dimensional Janus material constructed by the modeling method for two-dimensional Janus materials according to any one of claims 1-7 in predicting its structure and properties.

9. The application of the modeling method for two-dimensional Janus materials according to claim 8, characterized in that, Import the two-dimensional Janus material into the first-principles calculation software VASP, perform calculations using the generalized gradient approximation, set the energy cut-off value of the plane wave expansion to 400 eV, use VASPKIT to automatically generate high-symmetry points as K points while fixing the lattice, and generate a network along the high-symmetry points, where the electronic convergence accuracy is set to 1E-5 and the ionic convergence accuracy is set to 1E-2, and calculate the energy band and density of states of the two-dimensional Janus material.

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