Forces and atomic relaxation in density functional theory with the pseudopotential self-interaction correction

We present the scheme that allows for efficient calculations of forces in the framework of pseudopotential self-interaction corrected (pSIC) formulation of the density functional theory. The scheme works with norm conserving and also with ultrasoft pseudopotentials and has been implemented in the plane-wave basis code QUANTUM ESPRESSO. We have performed tests of the internal consistency of the derived expressions for forces considering ZnO and CeO2 crystals. Further, we have performed calculations of equilibrium geometry for LaTiO3, YTiO3, and LaMnO3 perovskites and also for Re and Mn pairs in silicon. Comparison with standard density functional theory (DFT) and DFT + U approaches shows that in the cases where spurious self-interaction matters, the pSIC approach predicts different geometry, very often closer to the experimental data.