High-pressure x-ray diffraction studies on HgTe and HgS to 20 GPa

HgTe and HgS have been investigated with the use of the high-pressure x-ray diffraction technique to 20 GPa. HgTe undergoes three pressure-induced phase transitions in the (0-20)-GPa range, from zinc blende to cinnabar to rocksalt to $\beta -\mathrm{Sn}$, at 1.4, 8, and 12 GPa, respectively. HgS does not show any evidence for a transition from the cinnabar structure up to 20 GPa, either in high-pressure x-ray diffraction or in high-pressure Raman studies. The above transition sequence agrees with the pressure-induced sequence for CdTe except for the intrusion of the cinnabar structure. Evaluation of the bulk modulus $B_0$ and $B_0^{\prime }$ from high-pressure x-ray data reveals that the cinnabar phases of HgTe and HgS are very compressible; $B_0$ and $B_0^{\prime }$ are 19.4±0.5 GPa and 11.1 for HgS, and 16.0±0.5 GPa and 7.3 for HgTe. Bulk moduli, volume changes for transitions, and lattice parameters of the high-pressure phases have all been determined from the x-ray data. The observed transition sequence for HgTe appears to be in agreement with the predictions of recent pseudopotential total-energy calculations for phase stability in III-V and II-VI compounds under pressure.