Pressure evolution of the potential barriers of phase transition of MoS2, MoSe2 and MoTe2

Abstract

Two-dimensional crystals with weak layer interactions, such as twisted graphene, have been a focus of research recently. As a representative example, transitional metal dichalcogenides show a lot of fascinating properties due to stacking orders and spin–orbit coupling. We analyzed the dynamic energy barrier of possible phase transitions in MoX₂ (X = S, Se and Te) with first-principles methods. In the structural transition from 2H_c to 2H_a, the energy barrier is found to be increased following an increase of pressure which is different from the phase transition in usual semiconductors. Among MoS₂, MoSe₂ and MoTe₂, the energy barrier of MoS₂ is the lowest and the stability of both 2H_c and 2H_a is reversed under pressure for MoS₂. It is found that the absence of a phase transition in MoSe₂ and MoTe₂ is due to the competition between van der Waals interaction of layers and the coulomb interaction of Mo and X in nearest-neighbor layer of Mo in both phases.