Converging difficult SCF cases with conjugate gradient density matrix search

Abstract

The possibility of converging difficult self constent field (SCF) cases with the conjugate gradient density matrix search (CGDMS) method is investigated. Density functional theory calculations using various functionals and basis sets were performed on CrC, Cr₂, UO₂(OH)₄ and UF₄ which we deem representative of molecules which have SCF convergence problems. From calculations on these molecules we found that CGDMS has better SCF convergence properties than diagonalization alone, while it is comparable with diagonalization in combination with an adequately chosen level shift.