Ab initio path integral Monte Carlo simulations of warm dense hydrogen

Understanding the properties of warm dense hydrogen [1] is of paramount importance for the modeling of astrophysical objects (giant planets, brown dwarfs, etc) and for the development of technological applications such as inertial fusion energy. Yet, the simultaneous presence of Coulomb correlations, partial ionization, quantum degeneracy and strong thermal excitations renders its accurate theoretical description challenging: a holistic approach that takes into account all of these effects without uncontrolled approximations is needed.

Here, I present new ab initio path integral Monte Carlo (PIMC) simulations of warm dense hydrogen [2,3], which have been obtained without the usual fixed-node approximation. While being computationally costly, these simulations give us access to a host of observables, most notably the linear density response and the related local field factors [3]. Finally, I discuss the direct connection between our simulations and upcoming x-ray Thomson scattering (XRTS) experiments with hydrogen, and the potential utility of the static density response function as a physical observable to quantify electronic localization around the ions.

[1] M. Bonitz et al., arXiv:2405.10627

[2] T. Dornheim et al., Journal of Chemical Physics 160, 164111 (2024)

[3] T. Dornheim et al., arXiv:2403.08570