| Two-dimensional materials have excellent physical and electronic properties and mechanical flexibility,and have important application prospects in electrical,optoelectronic and flexible sensing.The fifth main group of single-layer black phosphorus and arsenic has important application potential in micro-nano optoelectronic devices and defense electronic safety due to its unusual auxetic effect.It is a very meaningful study to evaluate the electronic properties and negative Poisson's ratio performance of single-layer black phosphorus/arsenic.The paper studies the single-layer black phosphorus and the first-principles method based on density functional theory.Intrinsic physical properties of arsenic,uniaxial strain and vertical electric field control the lattice constant,electronic structure and negative Poisson's ratio of single-layer black phosphorus/arsenic,and the electron and mechanics of different calculation methods for single-layer black phosphorus The impact of performance,the specific research content of this paper is as follows:1)Firstly,the first-principles method was used to calculate the lattice constant,electronic structure and dissociation energy of the bulk material formed by the AA and AB stacking methods of phosphorus/arsenic materials,the GGA-PBE and PBE+opt B88-vd W method was used to calculate the single phosphorus/arsenic phonon spectrum.2)On the lattice constant of the optimized black phosphorus/arsenic cell,a stable singlelayer black phosphorus/arsenic two-dimensional material is obtained by relaxation,and the single layer black phosphorus/arsenic is calculated by PBE and HSE methods respectively.The band gap value,and the band gap value calculated by the HSE method is found to be larger than the PBE method.In addition,the band gap value calculated by the PBE+opt B88-vd W method is slightly larger than the unadded value.3)After the crystal structure of the single-layer black phosphorus/arsenic is optimized and stabilized,the uniaxial strain in the range of ± 5% is applied along the zigzag,armchair and the vertical direction of the crystal structure,respectively,and the strain in three directions is found to be horizontal.Coordinate,the static total energy difference produced by the three uniaxial strain directions is a parabolic-like curve,which is consistent with the Hooke's law of mechanics.The stress generated by applying strain along the vertical direction is the largest,which is consistent with the vertical direction of freedom.The maximum and the other two directions of freedom are limited,and for the influence of uniaxial strain on the band gap,the single layer of black phosphorus tends to increase linearly in the direction of zigzag and armchair,while the single layer of arsenic decreases in the direction of the armchair.4)The application of uniaxial strain along zigzag,armchair and vertical direction has an effect on the structure of a single layer of black phosphorus/arsenic.It is found by calculation that there is a negative Poisson's ratio effect only in the zigzag direction and the vertical direction,and the single layer of black phosphorus and arsenic are in The negative Poisson's ratio(NPR)vac =-0.087/-0.125 and vca =-0.050/-0.172 in the zigzag direction and the vertical direction,we can see from the data that the negative Poisson's ratio effect in the zigzag direction is greater than the vertical direction.Because of the small degree of freedom in the zigzag direction,and the negative Poisson's ratio effect of arsenic is greater than that of phosphorus,we further explain the mechanism of the negative Poisson's ratio effect of black phosphorus/arsenic.5)For single-layer black phosphorus and arsenic,the uniaxial strain in zigzag and vertical direction has a reversible auxetic effect.When the vertical electric field strength is 6V/nm,the electric field control can be made when the GGA-PBE method is used.The negative Poisson's ratio(NPR)vac and vca of the single layer P/As increased by 22% / 32% and 28% / 70%,respectively.For the calculation of the PBE+opt B88-vd W method,the electric field regulation can make the single layer P / As negative Poisson's ratio(NPR)vac andvca increase by 12% / 20% and 23% / 35%,which means that the two layers of black phosphorus and arsenic have negative Poisson's ratio effect And vd W has a negative effect on the negative Poisson's ratio. |
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