Equation of state of carbon in the warm dense matter regime from density-functional theory molecular dynamics

Abstract

We show how orbital-free molecular dynamics can be regarded as the limit of quantum molecular dynamics at high temperature for the calculation of the equation of state of carbon. As a result, we construct an approach that allows to reproduce the quantum molecular dynamics equation of state of carbon at high temperature by combining quantum and orbital-free molecular dynamics. We apply this approach to a wide range of density and temperature conditions of the liquid or plasma state: $30\ensuremath{\ge}\ensuremath{\rho}\ensuremath{\ge}0.8\phantom{\rule{0.16em}{0ex}}\mathrm{g}/{\mathrm{cm}}^{3}, T\ensuremath{\ge}1$ eV. Then we test the sensitivity of the equation of state obtained to the choice of the exchange-correlation functional. We retain the generalized gradient approximation of this functional, corrected to approximately include the influence of temperature, and compare the results obtained to published first-principles calculations and to experimental shock data.