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The atomic geometry, structure stability, electronic and magnetic properties of VSe_2 were systematically investigated based on the density functional theory(DFT). Varying from 3D to 2D four VSe_2 structures, bulk 2H-VSe_2 and 1T-VSe_2, monolayer H-VSe_2 and T-VSe_2 are all demonstrated as thermodynamically stable by lattice dynamic calculations. More interestingly, the phase transition temperature is dramatically different due to the lattice size. Finally, owing to different crystal structures, H-VSe_2 is semimetallic whereas T-VSe_2 is totally metallic and also they have different magnetic moments. Our main argument is that being exfoliated from bulk to monolayer, 2H-VSe_2 transforms to T-VSe_2, accompanied by both semimetallic-metallic transition and dramatic magnetic moment variation. Our calculations provide a novel structure phase transition and an efficient way to modulate the electronic structure and magnetic moment of layered VSe_2, which suggests potential applications as high-performance functional nanomaterial.
The atomic geometry, structure stability, electronic and magnetic properties of VSe_2 were systematically investigated based on the density functional theory (DFT). Varying from 3D to 2D four VSe_2 structures, bulk 2H-VSe_2 and 1T-VSe_2, monolayer H-VSe_2 and T -VSe_2 are all demonstrated as thermodynamically stable by lattice dynamic calculations. More interestingly, the phase transition temperature is dramatically due due to the lattice size. Finally, owing to different crystal structures, H-VSe_2 is semimetallic whereas T-VSe_2 is totally metallic and Our main argument is that being exfoliated from bulk to monolayer, 2H-VSe_2 transforms to T-VSe_2, accompaniment by both semimetallic-metallic transition and dramatic magnetic moment variation. Our plans provide a novel structure phase transition and an efficient way to modulate the electronic structure and magnetic moment of the layered VSe_2, which suggests potential applications as hig h-performance functional nanomaterial.