The stability of the rhombohedral  -Hg phase alloyed with Sn under high pressure up to 30 GPa

Abstract

The effects of pressure on phase stability of an HgSn alloy with nearly equiatomic composition have been studied up to 30 GPa with diamond anvil cells using x-ray powder diffraction with synchrotron radiation. A Hg-rich phase hR 1-(Hg) with a rhombohedral distortion of a face-centred cubic (fcc) cell is found to form in the alloy at pressures above 3 GPa in coexistence with a Sn-rich phase with a simple hexagonal structure sh-hP 1 stable at ambient pressure. While the sh-hP 1 phase transforms at pressures above 15 GPa to a body-centred tetragonal bct-tI 2 phase, the hR 1-(Hg) phase remains stable up to 30 GPa. The hR 1-(Hg) phase is regarded as a solid solution of Sn in α-Hg. The range of solubility is estimated from about 5 to 10 at.% Sn. The alloying of Hg with Sn stabilises the α-Hg phase up to pressure of 30 GPa, while pure α-Hg becomes unstable at 3.7 GPa transforming to a bct (tI 2) phase. The hR 1-(Hg) phase reveals a strong anisotropy on compression. An increase of c/a from 1.99 to 2.25 in the pressure range from 2.6 to 29.9 GPa is observed displaying a trend towards fcc with c/a = 2.45 in a primitive rhombohedral setting (hexagonal axes). The stabilisation of the hR 1-(Hg) phase by alloying with Sn and the range of solubility of Sn in α-Hg are discussed within the concept of Fermi sphere–Brillouin zone interactions.

Simple Metal and Binary Alloy Phases Based on the fcc Structure: Electronic Origin of Distortions, Superlattices and Vacancies

“…The alloying of Hg with Sn under pressure was studied in [24]. The solubility of Sn in α-Hg was found to increase under pressure up to~10 at.…”

Simple Metal and Binary Alloy Phases Based on the <em>fcc</em> Structure: Electronic Origin of Distortions, Superlattices and Vacancies

“…The alloying of Hg with Sn under pressure was studied in [24]. The solubility of Sn in α-Hg was found to increase under pressure up to ~10 at.% Sn.…”