Relativistic Pseudopotentional Incorporating Core/Valence Polarization and Nonlocal Effects

Abstract

A relativistic pseudopotentional (RPP) for use in ab initio molecular electronic structure calculations is derived in the context of the relativistic effective core potential (REP) method of Lee et al. The resulting atom-specific RPP has salient features of the REP imbedded within it while retaining the form of a functional that is dynamically defined at runtime when used in calculations on molecules. The RPP is determined from Dirac-Fock wave functions for the isolated atom. Outer core two-electron interactions are incorporated into the RPP by means of variable coefficients that are defined in the context of the final molecular wave function. This form permits polarization of the outer core shells analogous to that occurring in all-electron molecular Hartree-Fock calculations while retaining these shells as part of the atomic pseudopotentional. Use of the RPP in post-Hartree-Fock molecular calculations permits the incorporation of core/valence correlation effects.

Nodeless Valence (Pseudo)spinors

“…Both of these effects are addressed using a procedure in which the outer cores, represented currently using VLC RECPs, are permitted to undergo a self-consistent field relaxation due to the molecular environment, that is, through a geometryand state-dependent functional called the relativistic pseudopotentional. 19 For example, the ability to incorporate six of the seven f subshell electrons in Am into the outer core leaves only three electrons that will require explicit treatment. It is seen in Table 6 that the splitting between the 5f 5/2 and 5f 7/2 ASs is 3 eV.…”

“…Thus, it is imperative to incorporate both the effects of core/valence polarization and the effects of nonlocal electron repulsion phenomena since these errors are large and are of opposite sign. Both of these effects are addressed using a procedure in which the outer cores, represented currently using VLC RECPs, are permitted to undergo a self-consistent field relaxation due to the molecular environment, that is, through a geometry- and state-dependent functional called the relativistic pseudopotentional . For example, the ability to incorporate six of the seven f subshell electrons in Am into the outer core leaves only three electrons that will require explicit treatment.…”