Structural transformations in a simple-hexagonal Hg-Sn alloy under pressure

The structure of Sn alloyed with Hg (10 at. %) was studied under pressure up to 66 GPa with energy-dispersive x-ray diffraction using synchrotron radiation. The ambient pressure simple hexagonal (hP1) phase transformed at 15 Cpa to a body-centered tetragonal (tI2) phase similar to the high-pressure forms of Sn and InBi. The axial ratio, cfa, of the tI2 phase increased with pressure up to a maximum value of c/a approximate to 0.92 at about 40 GPa and remained nearly constant upon further compression to 55 GPa. At pressures above 55 GPa, a second phase transition, probably to an orthorhombic phase, was observed. The structural trends observed are discussed in terms of a Fermi-sphere-Brillouin-zone interaction. [S0163-1829(99)04709-8].