Exploration of the Structural, Mechanical, Optical, Electronic, and Superconducting Properties of Boron–Carbon Clathrates MB2C8 (M = Na, K, Rb, Cs)

Abstract

At ambient pressure, the boron–carbon clathrate compounds have added a revolutionary drive to the research community by recent years to expand a new class of high-temperature superconducting materials. We have executed first-principles investigations on the structural configuration, mechanical parameters, Debye temperature, electronic properties, and superconducting nature of the boron–carbon clathrate MB₂C₈ (M = Na, K, Rb, Cs) compounds under pressure, up to 50 GPa. We also revealed the fundamental optical features of these compounds at 0 GPa. Our study discloses that these clathrates are mechanically stable under the studied pressures. Our study of Cauchy pressure, Poisson’s ratio, and Pugh’s ratio reveals that these materials are brittle at 0 GPa and tend to reach toward a ductile manner with increasing hydrostatic pressure. The NaB₂C₈ is found to exhibit ductile nature at and above 30 GPa and CsB₂C₈ at 50 GPa. The exploration of optical functions exhibits the metallic characteristics of these clathrates, which also support the investigation of the density of states and electronic band structure. Pressure-dependent characteristics of the superconductivity of these compounds are also observed, which show reasonable agreement with previous results.