High pressure equation of state studies using methanolethanolwater and argon as pressure media

We have measured the equation of state of the intermetallic compound AuIn₂ up to 20 GPa and Cd_0.8Hg_0.2 up to 50 GPa using methanolethanolwater solution or argon as pressure media. In the experiments performed with argon as pressure medium, we minimized non-hydrostatic conditions by thermally annealing the sample. We present data revealing compressibility anomalies in AuIn₂ at 2.7 GPa and in Cd_0.8Hg_0.2 near 8, 18 and 34 GPa with methanolethanolwater and argon. At pressures above 5 GPa the PV data for AuIn₂ and Cd_0.8Hg_0.2 from experiments preformed with argon as a pressure medium start deviating from those using methanolethanolwater, and the equation of state based on experiments in argon is stiffer compared with that in methanolethanolwater. This behavior is consistent with the relative merits of the two pressure transmitting media as documented in the literature. We also provide a brief summary of the results of electronic structure calculations that associate these anomalies with electronic topological transitions.