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

A 10-fold gold coordinated tetragonal structure is predicted for AuIn2 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 AuIn2 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 SiO2 and TiO2.