Study on conductivity properties and stability of NbAs based on first-principles

The properties of Weyl material NbAs are studied based on first principles in this paper. Firstly, the Visualizer module of Material Studio software is used to construct NbAs single-layer nanotube and nanobelt, and then CASTEP module is used to optimize and calculate the band structure, density of states and conductivity curves. The energy band, density of states and conductivity curves of carbon nanotube and nanobelt are compared. The results show that the energy band structure of NbAs has conduction band and valence band crossing at Fermi energy level, which shows obvious metallicity and is more conductive than graphene. Secondly, DMOL3 package is used to calculate and analyze the energy band and state density of NbAs nano-ribbon after adding positive and negative voltage along the armchair direction and zigzag direction, respectively. The results show that the valence band of NbAs nanobelt decreases when positive voltage is applied along the direction of the armchair, while increases when negative voltage is applied. When the voltage is applied at 0.05a.u., the peak values of the distribution curve of density of states increase from about 30 eV to 800 eV, and the peak values of the electron density of states increase significantly. When voltage is applied along the zigzag direction, either positive or negative voltage will cause the valence band to move down. When the negative voltage is -0.10a.u., the peak values of the density of states change obviously. Finally, the stability of NbAs is calculated and analyzed. It is found that NbAs nanobelt meet the requirement of stability of elastic modulus of hexagonal crystal system, but have weak shear resistance in plane (001). This indicates that the structure of NbAs is layered, similar to graphene, which is easier to be separated and detached in layers. This study can provide certain theoretical basis for our future experimental exploration of NbAs material properties.