Pressure induced superconductive 10-fold coordinated TaS: a first-principles study.

By crystal structure prediction and first-principles calculations, we researched the structure transformation and electronic states for a typical transition metal dichalcogenides (TMDs): 1T-TaS under hydrostatic pressure. The layered 1T-TaS will first transform to an 8-fold monoclinic C2/m phase and then to a 10-fold coordinated tetragonal I4/mmm phase which has 3D covalent bond network linked in space. Our calculations suggest that the lone pair electrons of S in 1T-TaS, which keep the stablity of the layered structure, will be activated by pressure and participate the chemical bonding with Ta, to form the high-pressure C2/m and I4/mmm phases. Additionally, collective electronic states of superconductivity also retains in the I4/mmm phase and the critical transition temperature of superconductivity is 9 K at 100 GPa.