Physically meaningful solutions of optimized effective potential equations in a finite basis set within KS-DFT framework

Abstract

The numerical evidence is provided showing that the physical solutions, in a finite basis set, of the optimized effective potential equations (OEP) in the context of the Kohn-Sham Density Functional Theory (KS-DFT) can only be obtained by employing the proper regularization procedure in the OEP method together with a judicious choice of basis sets used in the KS OEP calculations. The regularisation relies on the truncated singular value decomposition procedure to obtain the pseudoinverse of the density-density response matrix. We are showing that this is a critical aspect in determining the stable and numerically accurate solutions of the KS-OEP equations for the exchange-only and correlated cases.