Large effects of subtle electronic correlations on the energetics of vacancies in α -Fe

We study the effect of electronic Coulomb correlations on the vacancy formation energy in paramagnetic α-Fe within ab initio dynamical mean-field theory. The calculated value for the formation energy is substantially lower than in standard density-functional calculations and in excellent agreement with experiment. The reduction is caused by an enhancement of electronic correlations at the nearest neighbors of the vacancy. This effect is explained by subtle changes in the corresponding spectral function of the d electrons. The local lattice relaxations around the vacancy are substantially increased by many-body effects.