Role of nonspherical double counting in DFT+DMFT: Total energy and structural optimization of pnictide superconductors

A simple scheme for avoiding nonspherical double counting in the combination of density functional theory with dynamical mean-field theory (DFT+DMFT) is developed. It is applied to total-energy calculations and structural optimization of the pnictide superconductor LaFeAsO. The results are compared to a recently proposed ``exact'' double-counting formulation. Both schemes bring the optimized Fe-As interatomic distance close to the experimental value. This resolves the long-standing controversy between DFT+DMFT and experiment for the structural optimization of LaFeAsO.