Crystal structures of CsSi6 at high pressures

Abstract

High pressure is well known to be a useful tool to explore novel crystal structures of materials with unique chemical and physical properties that are not possible to access at ambient conditions. We here report some interesting crystal structures of CsSi6 using a global structure search at a pressure range of 0–30 GPa. Remarkably, we identify a new cubic Im-3m phase of CsSi6 at ambient conditions, and that phase undergoes to an orthorhombic Cmcm phase at ∼8.2 GPa, then transforms to a monoclinic C2/m phase at ∼20.8 GPa. It is found that Si atoms have 5-fold coordination in the high-pressure C2/m phase. These newly predicted structures are all dynamically stable, and their electronic properties are well presented in this work. The present results clearly show some interesting crystal structures of CsSi6 under high pressure, providing insights for exploring other high-pressure behaviors of alkali metal silicides.