The energetic effects of p, d, and f Gaussian polarization functions on closed‐shell AH_n oxygen and sulfur hydrides

Abstract

AbstractsA series of LCAO-MO-SCF calculations, using various basis sets of Gaussian-type functions, has been made in order to study the effects of p, d , and f polarization functions for a 10-electron isoelectronic series of oxygen hydrides and for an 18-electron isoelectronic series of sulfur hydrides. Conclusions from these results suggest that meaningful proton affinities cannot be calculated without the inclusion of a d function on the heavy atom and a p function on the hydrogen atoms. Theoretical BackgroundIn the terminology of modern quantum chemistry, the "completeness" of a basis set has, by necessity, implied the "infinite" nature of the same basis set. For example, a molecular Hartree-Fock (HF) orbital (4) can only be generated by an expansion in terms of an infinite number of atomic orbitals (AO) (7)Since all AO consist of both radial and angular parts, the infinite set should include all types of AO (s, p , d, f, g, h, . . .).

Molecular orbital study of some protonated bases

“…The relative stabilities of pairs of isomers are similar at Hartree-Fock and fourth-order Moller-Plesset theory, except for the C-and O-protonated forms of C=0. However, the Hartree-Fock barrier to proton transfer which separates the isomers is lowered by [11][12][13][14][15][16][17][18] kcal/mol by electron correlation. The Hartree-Fock barriers to proton transfer between lone-pair protonation sites in ions H"AAHn+1+ are also significantly lowered by correlation except for N2H+.…”