<i>Ab initio</i> effective core potentials for molecular calculations. Potentials for K to Au including the outermost core orbitals

TLDR

Ab initio effective core potentials were generated to replace the innermost core electrons of third‑ to fifth‑row atoms while treating the outermost core ns²np⁶ orbitals explicitly. The potentials include mass–velocity and Darwin relativistic corrections, are provided as analytic fits for multicenter integral evaluation, and are accompanied by Gaussian valence basis sets for the relevant s, p, and d orbitals. These ECPs enable accurate molecular calculations that require explicit treatment of outer core orbitals rather than their replacement by a core potential.

Abstract

Ab initio effective core potentials (ECP’s) have been generated to replace the innermost core electron for third-row (K–Au), fourth-row (Rb–Ag), and fifth-row (Cs–Au) atoms. The outermost core orbitals—corresponding to the ns2np6 configuration for the three rows here—are not replaced by the ECP but are treated on an equal footing with the nd, (n+1)s and (n+1)p valence orbitals. These ECP’s have been derived for use in molecular calculations where these outer core orbitals need to be treated explicitly rather than to be replaced by an ECP. The ECP’s for the forth and fifth rows also incorporate the mass–velocity and Darwin relativistic effects into the potentials. Analytic fits to the potentials are presented for use in multicenter integral evaluation. Gaussian orbital valence basis sets are developed for the (3s, 3p, 3d, 4s, 4p), (4s, 4p, 4d, 5s, 5p), and (5s, 5p, 5d, 6s, 6p) ortibals of the three respective rows.