Orthogonalising Pseudo-Potentials in electronic structure calculations

An investigation of the Orthogonalising Pseudo-Potential (OPP) introduced b y Kukulin and Krasnopolsky is made with the emphasis on its numerical appli cation. The OPP method is a projection operator technique to remove unwante d stales from a many body calculation. An analysis of a model two level sys tem was used to deduce the basic properties of the spectrum of the projecte d Hamiltonian. Detailed plots of the atomic properties of Na, Na-, Nae(+) a nd NaPs were made as a function of the strength of the OPP to exhibit the o peration of the OPP procedure for some complicated many-body systems. An im proved wave function for the NaPs ground state was generated as a byproduct of this investigation. The current best estimates of the NaPs binding ener gy and annihilation rate are 0.008009 Hartree and 2.072 x 10(9) s(-1), resp ectively (C) 1999 Elsevier Science B.V, All rights reserved.