Phase Transition Of Transition Metal Dichalcogenides Under High Pressure

The article studies the changes in matter under high pressure and discovers the high-pressure structures of some transition metal dichalcogenides(TMDs)and their corresponding physical characteristics.In addition,these findings also help us understand the physical properties of the internal structure of the planet(Earth).At present,layered materials TMDs have some interesting characteristics under high pressure,such as charge density waves,superconductivity and topology.The emergence of these characteristics has greatly encouraged people's research interest in this kind of materials.The TaS₂ and TiTe₂ we studied are a two-layer X-W-X sandwich structure type under ambient pressure.The atoms between each single layer are combined by weak Van der Waals force.We know that by continuously increasing the pressure(hydrostatic pressure),the crystal structure and electronic characteristics of the material can be effectively adjusted.In this paper,the CALYPSO structure search software is used to search the global domain minimum structure under different pressures(0 GPa-100 GPa).At the same time,based on the density functional theory and density functional perturbation theory,the ab initio calculation(VASP)software package is used.Projection augment wave(PAW)method,aeneralized gradient approximation(GGA)theory and QUANTUM ESPRESSO software package were used to theoretically study the structural phase transition and electronic structure of(TaS₂and Ti e₂)transition metal disulfide under high pressure.The transition metal disulfide has been confirmed to be the P-3m1 phase(eg:TiS₂,TiTe₂,TiSe₂)at room pressure,and our results show that the transition metal disulfide(TaS₂ and TiTe₂)will change to the C2/m phase with increasing pressure,and with further pressure,the C2/m phase will turn into I4/mmm phase or Fe₂P-type(P-62m)phase.We find that transition metal disulfide basically has a C2/m phase with increasing pressure,which indicates that C2/m is a common transition phase with respect to transition metal disulfides.This also shows that as the pressure increases,the volume of the substance will be compressed,and the interaction between atoms will be strengthened,which will also increase the number of bonds between atoms.We have verified through calculation that the kinetics of the structure of the transition metal disulfide material after phase change under high pressure can exist stably.Finally,we find that transition metal disulfides also show superconductivity after undergoing phase transition under high pressure.For example,the calculated superconducting transition temperature(Tc)of the I4/mmm phase at 100 GPa is around 9 K.