Reconstruction of frozen-core all-electron orbitals from pseudo-orbitals

We investigate the numerical feasibility of reconstructing frozen-core all-electron molecular orbitals from corresponding pseudo-orbitals. We perform density-functional calculations on simple atomic and molecular model systems using ultrasoft pseudopotentials to represent the atomic cores. We apply a transformation due to Blochl [Phys. Rev. B 50, 17953 (1994)] to each calculated pseudo-orbital to obtain a corresponding frozen-core all-electron molecular orbital. Our model systems include the reconstruction of the 5d orbital of a gold atom, and the occupied valence states of the TiO2 molecule. Comparison of the resulting all-electron orbitals to corresponding ones that were obtained from calculations in which the core electrons were explicitly included indicates that all-electron molecular orbital reconstruction is a feasible and useful operation in reproducing the correct behavior of molecular orbitals in the nuclear core regions. (C) 2001 American Institute of Physics.