Phase Transition and EOS of Cinnabar (α-HgS) at High Pressure and High Temperature

Abstract

Phase relations and equation of state (EOS) of natural cinnabar (α-HgS) are investigated by high-pressure and high-temperature synchrotron x-ray powder diffraction. The unambiguous cinnabar–rocksalt structure phase boundaries are determined to be Plower (GPa) = 15.54 – 0.014T(°C) and Pupper(GPa) = 23.84 – 0.014T(°C) at 300–623K. With K′ fixed at 4, we obtain K0 = 37(4)GPa, (δK/δT)P = −0.025(2) GPaK−1, and α0 = 3.79(20) × 10−5 K−1 for the cinnabar phase of α-HgS. The (δK/δT)P and α0 of cinnabar phase are obtained for the first time. A nearly isotropic compression of cinnabar phase is observed by linear regressions.