Prediction of a novel 10-fold gold coordinated structure in AuIn₂ above 10 GPa

Abstract

A 10-fold gold coordinated tetragonal structure is predicted for AuIn above 10 GPa by employing the first-principles crystal structure search method. This structure remains the lowest enthalpy structure up to the highest pressure of this study. Detailed electronic structure analysis is carried out to figure out the underlying factors responsible for the transition. Pressure induced electronic topological transition is found to be one of the main factors behind this transition. Phonon calculations show the softening of TA mode phonons and destruction of the giant Kohn anomaly in close proximity to the transition. Bader charge analysis shows the charge transfer increase from the In to Au atom under pressure. So this study has solved a long-standing structural puzzle of the AuIn above 10 GPa. This study is also expected to play an important role in our understanding of the pressure induced metallization of geophysically relevant oxides such as SiO and TiO.

Structural Phase Transitions in PtIn2 at High Pressure: A Theoretical Investigation

“…It is also evident that the phonon (Figure , 0 and 12 GPa) in PtIn 2 shows usual pressure hardening, ruling out any possibility of the phonon softening in the ambient-pressure phase. Contrary to this, phonon softening was predicted in the CaF 2 -type phase of AuIn 2 close to the transition …”

“…It is also evident from Figure that near 10 GPa the enthalpy of the orthorhombic Pnma structure becomes lower compared to the ambient CaF 2 -type structure but remains higher compared to the Fe 2 B-type structure and, hence, is consistent with our earlier calculations. Note that AuIn 2 also adopts the Fe 2 B-type structure at ∼10 GPa …”

“…The electronic properties of different phases are analyzed by calculating the band structure, DOSs, and electron-localization functions (ELFs; Figures and ). The overall band structure of the CaF 2 -type PtIn 2 is very similar to that of AuIn 2 . Because Pt has one electron less than Au, the Fermi level moves down, leaving one band partially empty in PtIn 2 .…”

“…Here we studied the high-pressure structural properties of PtIn 2 , which crystallizes in the CaF 2 -type structure and has many important industrial applications. − It is observed that, in CaF 2 -type structure intermetallics, the constituent elements have nearly identical atomic sizes, and, hence, charge transfer, due to the electronegativity difference, plays an important role in their structural stability . Recently, we predicted a structural transition from CaF 2 -type structure to Fe 2 B-type tetragonal structure in AuIn 2 near 10 GPa . An electronic topological transition (ETT) was thought to be responsible for this structural transition.…”

“…13 Recently, we predicted a structural transition from CaF 2 -type structure to Fe 2 B-type tetragonal structure in AuIn 2 near 10 GPa. 18 An electronic topological transition (ETT) was thought to be responsible for this structural transition. Pt has one less valence electron than Au, and according to the Hume−Rothery rule, 3 the average valence electron density (average valence electron/atom) plays an important role for the phase stability of alloys and intermetallics.…”