Virial expansion of the electrical conductivity of hydrogen plasmas.

The low-density limit of the electrical conductivity $\ensuremath{\sigma}(n,T)$ of hydrogen as the simplest ionic plasma is presented as a function of the temperature $T$ and mass density $n$ in the form of a virial expansion of the resistivity. Quantum statistical methods yield exact values for the lowest virial coefficients which serve as a benchmark for analytical approaches to the electrical conductivity as well as for numerical results obtained from density functional theory--based molecular dynamics simulations (DFT-MD) or path-integral Monte Carlo simulations. While these simulations are well suited to calculate $\ensuremath{\sigma}(n,T)$ in a wide range of density and temperature, in particular, for the warm dense matter region, they become computationally expensive in the low-density limit, and virial expansions can be utilized to balance this drawback. We present new results of DFT-MD simulations in that regime and discuss the account of electron-electron collisions by comparison with the virial expansion.