LAUSR

Abstract By adopting the first-principles methods based on the density functional theory, we studied the electronic and magnetic properties of group-V MX2 (M = V, Nb, Ta; X = S, Se, Te) monolayers with atomic-sized structural defects. We firstly studied the two phases of 1H and 1T. It shows that the formation energies of the 1T phase are lower compared with those of the 1H phase for VSe2 and VTe2. For the rest MX2, the formation energies of the 1H phase are lower. Our results indicate that all the 1H and 1T phases of MX2 are metal except for 1H-VSe2 and 1H-VTe2 which are semiconducting. For monolayers MX2 with atomic-sized defects, our calculations predict that the diatomic X atoms vacancies of VX-X and V2X both cause the metal–semiconductor transition, and vacancies of VM and VX-X, as well as anti-site defect of MX induce semiconductor–metal transition. Meanwhile, the total magnetic moments of the 1H and 1T phases of VX2 increase with inducing the X atom vacancies including VX, VX-X and V2X. Additionally, VX vacancy and V2X vacancy bring magnetism into the 1T-TaSe2 and 1T-TaS2, respectively.