Xavier Andrade, Lawrence Livermore National Laboratory
In this presentation, I explore the application of real-time electron dynamics, the explicit simulation of the quantum dynamics of electrons in time, to study the conduction of electricity in metals. These simulations give us access to many current related properties, in particular, the calculation of electrical conductivities in different regimes.
We have implemented this approach using time-dependent density functional theory (TDDFT) in its real-time formalism. This implementation allows us to induce, measure and visualize the current density as a function of time in realistic systems. The computational efficiency of the method allows us to perform simulations with hundreds and even thousands of atoms.
We have found that real-time TDDFT can describe how currents naturally decay in metals, and from this dissipation process we can directly calculate the frequency-dependent conductivity, including the direct current (DC) conductivity that is not accessible from linear-response approaches like Kubo-Greenwood. Since our method deals with finite-intensity electric fields, we gain access to properties beyond the linear regime for intense electric fields and current densities.
We illustrate our approach by simulating the linear and non-linear conductivity of aluminum at high temperature. Our calculations predict that the conductivity of liquid aluminum changes for very-high currents and that it even exhibits negative differential conductivity.