Chinese Acad Sci, Beijing Synchrotron Radiat Facil, Inst High Energy Phys, Beijing 100049, Peoples R China
The phase transition kinetics of HgS from cinnabar to rocksalt structure under high pressure was studied by first-principle computations. The calculations have been performed using the density functional theory (DFT) and the augmented plane wave (APW) plus local orbitals (LO) basis set. The calculations clarify the argument about the phase transition pressure and verify it is a second-order phase transition theoretically. The results also describe the variations of parameters a, c, c/a and the atom fractional coordinates u and v during the phase-transition process. The simulation of the atomic configurations under different pressures depicts the phase-transition process as two steps, i.e., the relaxation and reconstruction of the Hg-S helical chains.