Electrical Conductivity of Hydrogen Plasmas: Low-density Benchmarks and Virial Expansion Including $e-e$ Collisions

An improved virial expansion for the low-density limit of the electrical conductivity $\sigma (T,n)$ of hydrogen as the simplest ionic plasma is presented. Quantum statistical methods provide exact values for the lowest virial coefficients, which serve as a benchmark for analytical approaches to electrical conductivity as well as for numerical results from density functional theory based molecular dynamics simulations (DFT-MD) or path-integral Monte Carlo (PIMC) simulations. The correction factor introduced by Reinholz {\it et al.}, Phys. Rev. E {\bf 91}, 043105 (2015) is applied to describe the inclusion of electron-electron collisions in DFT based calculations of transport coefficients. As a benchmark, the first virial coefficient is correctly described with this approach. The value of the second virial coefficient is discussed, questions about its value according to DFT-MD simulations are addressed.