Noblest of All Metals Is Structurally Unstable at High Pressure

Abstract

In a series of experiments in externally electrically heated diamond anvil cells we demonstrate that at pressures above approximately 240 GPa gold adopts a hexagonal-close-packed structure. Ab initio calculations predict that at pressures about 250 GPa different stacking sequences of close-packed atomic layers in gold become virtually degenerate in energy, strongly supporting the experimental observations.

Synthesis of hexagonal close-packed gold nanostructures

“…Recently, hcp Au with stacking faults was observed in the catalyst used for the heterogeneous growth of germanium nanowires 37 . Under certain extreme conditions, such as ultrahigh pressure, an fcc Au can also transform to its hcp structure 38 . To the best of our knowledge, this is the first time an AuNS has been directly synthesized, which is exclusively in the hcp phase, with the unique square-sheet morphology and stable under ambient conditions.…”

Simple metal and binary alloy phases based on the hcp structure: Electronic origin of distortions and superlattices

“…Thus in pure elements Cu and Ag fcc is found to be stable up to 190 GPa and 92 GPa, respectively [8] and for Au the fcc -hcp transition was found above 250 GPa with nearly ideal axial ratio c/a = 1.63 [20].…”

“…The Cu 20 Zn 80 phase is one of the representative Hume-Rothery phases, called as , occurring at electron concentration z ~ 1.8. Structural data and parameters of the FS-BZ configuration are given in Table 1 and presented in Fig.1b.…”

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

“…It should be noted that only for Au was the fcc-hcp transition experimentally observed above 250 GPa [22].…”