Two-temperature equation of state for aluminum and gold with electrons excited by an ultrashort laser pulse

A short laser pulse converts metal into a two-temperature state with the electron temperature higher than the ion temperature. To describe the electron contributions to the total internal energy and pressure arising as a result of electron heating, we develop the new analytic approximation formulae for two-temperature thermodynamics of metal. Those approximations are based on quantum calculations performed with density functional theory (DFT) packages. DFT calculations provide the internal energies and pressures for densities of the order of solid-state density and for electron temperatures up to 55 kK. The new analytic approximations give a better accuracy in hydrodynamic simulation of laser-matter interaction and should be used instead of the less accurate expressions based on the Fermi model of ideal electron gas, which is widely used for two-temperature states of metal.