Title: First-principles prediction of the stacking fault energy of gold at finite temperature,
Abstract: The intrinsic stacking fault energy (ISFE) $\gamma$ is a material parameter
fundamental to the discussion of plastic deformation mechanisms in metals.
Here, we scrutinize the temperature dependence of the ISFE of Au through
accurate first-principles derived Helmholtz free energies employing both the
super cell approach and the axial Ising model (AIM). A significant decrease of
the ISFE with temperature, $-(36$-$39)$\,\% from 0 to 890\,K depending on the
treatment of thermal expansion, is revealed, which matches the estimate based
on the experimental temperature coefficient $d \gamma / d T $ closely. We make
evident that this decrease predominantly originates from the excess vibrational
entropy at the stacking fault layer, although the contribution arising from the
static lattice expansion compensates it by approximately 60\,\%. Electronic
excitations are found to be of minor importance for the ISFE change with
temperature. We show that the Debye model in combination with the AIM captures
the correct sign but significantly underestimates the magnitude of the
vibrational contribution to $\gamma(T)$. The hexagonal close-packed (hcp) and
double hcp structures are established as metastable phases of Au. Our results
demonstrate that quantitative agreement with experiments can be obtained if all
relevant temperature-induced excitations are considered in first-principles
modeling and that the temperature dependence of the ISFE is substantial enough
to be taken into account in crystal plasticity modeling.