  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.
