Lattice stability of ultrafast-heated gold

First principle simulations within the framework of the finite-temperature density functional formalism predict the existence of nonthermal phase transitions in gold on ultrafast timescales with increasing electron temperature. The Gibbs free energy phase diagram as a function of electronic temperature indicates two solid-solid phase transitions of fcc→hcp at an electronic temperature of 1.2 eV and hcp→bcc at an electron temperature of 6.8 eV, while the ion lattice remains cold at zero temperature. We present a detailed analysis of the process of phonon-hardening in ultrafast-heated gold, using finite-temperature density functional perturbation theory simulations of the phonon spectra, the quantum thermodynamic phase diagram, and the thermoelastic properties.