Face-centred cubic to tetragonal transitions in In alloys under high pressure

The effect of pressure on the structural behaviour of In alloys with Cd, Sn and Pb has been studied with diamond anvil cells using synchrotron radiation. The face-centred cubic phase (fcc) of an In alloy with 6 at% Cd transforms under pressure into a face-centred tetragonal In-type phase, fct, with c / a >1. The fcc phases of In alloys with 40 and 60 at% Pb transform under pressure to fct with c / a <1. For the ambient pressure fct phase ( c / a <1) of an In alloy with 20 at% Sn the distortion increases with pressure. The stability of the tetragonal phases under pressure with respect to the cubic structure is discussed in terms of Brillouin-zone-Fermi-sphere interaction.