First-principles prediction of pressure dependent mechanical, electronic, optical, and superconducting state properties of NaC6: A potential high-Tc superconductor

TL;DR

This study uses first-principles calculations to explore the pressure-dependent properties of NaC6, revealing its potential as a high-temperature superconductor with stable structures at high pressures and detailed insights into its electronic, optical, and superconducting characteristics.

Contribution

It provides the first comprehensive analysis of NaC6's thermophysical, elastic, electronic, optical, and superconducting properties under pressure, including new insights into its stability and optoelectronic spectra.

Findings

NaC6 is structurally stable only above 40 GPa.

NaC6 exhibits metallic behavior with high ductility.

Superconducting transition temperature varies with pressure, exceeding 100 K at certain conditions.

Abstract

Very recently carbon-rich NaC6 with sodalite-like structure has been predicted to show superconducting transition temperature above 100 K at relatively low applied (compared to high-Tc hydrides) hydrostatic pressures. We have investigated the pressure dependent structural, elastic, electronic, superconducting state, and optoelectronic properties of NaC6 in this study. Some important thermophysical properties have also been explored. The elastic properties along with Poisson's and Pugh's ratios and optoelectronic parameters are investigated for the first time. NaC6 was found to be structurally stable only at high pressures at and above 40 GPa, in agreement with previous study. The compound is highly ductile and the chemical bonding is predominantly metallic in nature. The Debye temperature shows strong pressure dependence. The Gruneisen parameter also exhibits significant pressure dependence. The electronic band structure reveals metallic character and consists of highly dispersive and almost flat bands crossing the Fermi level. Both the electronic density of states at the Fermi level and repulsive Coulomb pseudopotential increase gradually with increasing pressure in the range 40 GPa to 70 Gpa. The degree of dispersion in the E(k) curves depend weakly on pressure both in the valence and conduction bands. The optical parameters spectra, studied for the first time, correspond well with the electronic band structure. NaC6 absorbs and reflects electromagnetic radiation quite efficiently in the mid-ultraviolet region. Superconducting transition temperatures of NaC6 have been estimated at different pressures and compared with previously reported values. The effects of various parameters on Tc have been discussed in details.