Novel Topological Motifs and Superconductivity in Li-Cs System.

Abstract

In this work, we determined the phase diagram and electronic properties of the Li-Cs system by using an evolutionary crystal structure prediction algorithm coupled with first-principles calculations. We found that Li-rich compounds are more easily formed in a wide range of pressures, while the only predicted Cs-rich compound LiCs₃ is thermodynamically stable at pressures above 359 GPa. A topological analysis of crystal structures concludes that both Li₆Cs and Li₁₄Cs have a unique topology that has not been reported in existing intermetallics. Of particular interest is the fact that four Li-rich compounds (Li₁₄Cs, Li₈Cs, Li₇Cs, and Li₆Cs) are found to be superconductors with a high critical temperature (∼54 K for Li₈Cs at 380 GPa), due to their peculiar structural topologies and notable charge transfer from Li to Cs atoms. Our results not only extend an in-depth understanding of the high-pressure behavior of intermetallic compounds but also provide a new route to design new superconductors.