Band structure, Fermi surface, superconductivity, and resistivity of actinium under high pressure

Abstract

The electronic band structures of fcc actinium (Ac) have been calculated for a wide range of pressures by reducing the unit-cell volume from $1.0{V}_{0}$ to $0.5{V}_{0}$ with use of the relativistic augmented-plane-wave method. The density of states and Fermi-surface cross sections corresponding to various volumes are obtained. Calculations for the band-structure-related quantities such as electron-phonon mass enhancement factor $\ensuremath{\lambda}$, superconducting transition temperature ${T}_{c}$, and resistivity $\ensuremath{\rho}$ corresponding to different volumes are performed. It is seen that ${T}_{c}$ increases with pressure, i.e., with decreasing volume. A new empirical relation for the volume dependence of ${T}_{c}$ is proposed and its validity is checked using the ${T}_{c}$ values obtained from the above band-structure results. The resistivity $\ensuremath{\rho}$ first increases with increasing pressure (i.e., with decreasing volume) and then decreases for higher pressures (i.e., for smaller volumes).