The role of non-spherical double counting in DFT+DMFT: total energy and structural optimization of pnictide superconductors

TL;DR

This paper introduces a new scheme to correct non-spherical double counting in DFT+DMFT calculations, improving structural predictions of pnictide superconductors and resolving previous discrepancies with experimental data.

Contribution

A simple, effective scheme for avoiding non-spherical double counting in DFT+DMFT, applied to LaFeAsO, aligning theoretical results with experimental structural data.

Findings

Both schemes yield Fe-As distances close to experiments

Resolves controversy between DFT+DMFT and experimental structural optimization

Improves accuracy of total energy calculations in pnictide superconductors

Abstract

A simple scheme for avoiding non-spherical double counting in the combination of density func- tional 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 stand- ing controversy between DFT+DMFT and experiment for the structural optimization of LaFeAsO.