Speaker
Description
We combine ab initio path integral Monte Carlo (PIMC) simulations with fixed ionic
configurations, obtained by DFT-MD simulations, in order to solve the electronic problem
for hydrogen under warm dense matter conditions. To solve the divergence problem in
the Ewald-sum for attractive potentials we employ the pair-approximation. This approach
is compared against the much simpler Kelbg pair-potential. We find very favorable
convergence behavior towards the former. Since PIMC does not require any further
assumptions regarding exchange and correlations of the many-body system, we then
compare electronic densities obtained from our snapshot PIMC calculations with DFT
calculations in the metallic regime. Furthermore, we investigate the manifestation of the
resulting fermionic sign problem in our snapshot PIMC simulations. This gives us the
unique capability to study the properties of warm dense hydrogen from ab initio
simulations without any further assumptions, like the functional form of the exchange-
correlation effects or fixed fermionic nodes. Thus, snapshot PIMC enables us to obtain
the exact density response of warm dense hydrogen. This is extremely valuable to both
experiments, like X-Ray Thomson scattering, as well as the development of new XC-
functionals.
