The electronic band structures of fcc actinium (Ac) have been calculated for a wide range of pressures by reducing the unit-cell volume from $1.0V_0$ to $0.5V_0$ 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 $\lambda$, superconducting transition temperature $T_c$, and resistivity $\rho$ 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 $\rho$ first increases with increasing pressure (i.e., with decreasing volume) and then decreases for higher pressures (i.e., for smaller volumes).

• Received 20 March 1984

DOI:https://doi.org/10.1103/PhysRevB.30.6943