Exploration of potassium silicide compounds under high pressure

Abstract

Herein, we have performed extensive swarm-intelligence structures searching simulations on the KSix (x = 4, 5, 6, 7, 8) compounds within the pressure range from 0 to 50 GPa. Seven crystal structures of potassium silicides are proposed, and the dynamic stability of these phases were explored in the corresponding pressure range. KSi4 was predicted to be stable, and it was found to have two phases, named C2/m-a and C2/m-b, respectively. As for KSi5, two thermodynamically stable phases were determined as C2/m and Imma, respectively. Above 1.33 GPa, the proposed monoclinic phase with C2/m is energetically favorable. With the increasing pressure, our proposed new Imma phase becomes energetically favorable at 16 GPa. For KSi6, it was determined that has the following space groups, Cmcm, C2/m and P6/m. These findings provide insights for helping advance our understanding of the KSix compounds under high pressure.