Electrical-conductivity calculation in ab initio simulations of metals:Application to liquid sodium

We describe a calculation of the electrical conductivity in ab initio simulations of liquid sodium, using the Kubo-Greenwood formula for the optical conductivity and the molecular-dynamics scheme based on finite-temperature density functional theory. The effect of different Brillouin-zone samplings and that of the finite size of the system have been extensively studied at different temperatures. Close to the melting point, even with an adequate sampling of the Brillouin zone, our results exhibit a large discrepancy between theory and experiment. This is much reduced at higher temperatures. The possible reasons for this behavior are discussed.