Nonempirical s.c.f. calculations on sulfur atom, hydrogen sulfide, and dihydrogen sulfoxide

Abstract

This paper reports the f i s t attempt to use Gaussian basis sets in nonempirical self-consistent field (s.c.f.) calculations on sulfur-containingchemical systems. Exponents for Gaussian-type functions (G.t.f.) on S atom are given for the minimal basis set. The optimization procedure is described and the optimized exponents utilized on calculations on S atom, H2S, and the hypothetical dihydrogen sulfoxide (H2SO). Calculations by the minimal basis set of G.t.f., using these exponents, gave a value for the HSH angle of H2S that agrees well with the experimentally determined value. Calculations of H,SO support a "multiple bond" picture of the S-0 bond.Canadian Journal of Chemistry, 46, 1205Chemistry, 46, (1968 Introduction Ab initio calculations on atoms and small molecules are well established in the chemical literature (1). Accurate results have been obtained usingexponential-type functions (e.t.f.) or, as usually referred to, Slater-type orbitals (S.t.0.) as basis functions in the s.c.f. procedure. Satisfactory results have also been obtained using Gaussian-type functions (G.t.f.) or, as sometimes called, Gaussian-type orbitals (G.t.o.), when the basis set size is approximately 2 to 3 times as large as the equivalent basis set of e.t.f. (2). Methane, as a classical example, may be quoted for comparison of the numerical results obtained from e.t.f. and G.t.f. basis sets (3)(4)(5)(6)(7)(8). These results are shown in Table I. A compendium of ab initio calculations covering the period of 1960-67 which includes results of both e.t.f. and G.t.f. calculations has been prepared (9). Because it is possible to compute integrals over a basis of G.t.f. about 1000 times faster than over e.t.f., it appears advantageous to use the former, especially when the number of electrons in the problem becomes large. Even with this device it may still be necessary to employ a basis set that is less than adequate for quantitative purposes.Our primary interest is in the sulfinyl grouping (10). Because even the simplest sulfoxide, H,SO (I), represents a 26-electron problem containing four atoms, it was clear at the outset that a minimal basis set of G.t.f. had to be utilized. Exponents for the S atom were unknown because no S-containing compounds had been previously treated with G.t.f. It was necessary therefore to obtain first an optimal set of exponents for stype and p-type functions from open shell s.c.f. calculations on S atom in its electronic ground (3P) state and the exponent for d-type functions from closed shell s.c.f. calculations on H,S. This paper reports these results. To complete this preliminary study we have also performed closed shell s.c.f. calculations on 1.The mathematical formalism for the open and closed shell s.c.f. as well as other calculations (dipole moment, population analysis, and electron density contour plots) have been reviewed recently (11) 46, 1968 results obtained from computations on S, H2S, and H 2 S 0 are given in this paper. The computations have been carried out on an IBM 7094-11 computer usin...

Some Comments on the Conformations of Methyl Phenyl Sulfides, Sulfoxides and Sulfones

“…Orbital Orbital-type IT"/ eV "0 -( 4 s ) 12.57 This assignment is supported by their own CNDO/2 calculations, the ab initio calculations by Rauk & Czizmadia for H 2 S 0 [21] and, above all, by extensive correlation with the photoelectron spectroscopic results for many other sulfoxides [21].…”

Investigation of the basis of the valence shell electron pair repulsion model by ab initio calculation of geometry variations in a series of tetrahedral and related molecules

“…This of course, has been previously noted. 24 Bond lengths are also well reproduced with use of the complete basis set, the worst case being SF3, where the disagreement is 0.028 A. Omission of polarization functions on the central atoms yields excessively long calculated bond lengths to fluorine and oxygen ligands while the effect on bonds to hydrogen atoms is quite small. It should be noted that the calculated and experimental bond lengths are not strictly comparable.…”

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

“…One may also note from Table I11 that for neutral and positively charged hydrides, an [spdlsp] basis set is energetically more favourable than an [spdfls] basis set. Although the opposite is true for the diatomic anions [3] Table IV shows that the average energy contribution of an f function to an [spdls] basis set is always much smaller than the contribution of a p function to an [spdls] basis set. For example, in OH-, each of the nine contributing f functions lowers the energy by 0.000659 Hartree whereas each of the three contributing p functions lowers the energy by 0.001898 Hartree.…”

“…It should be noted, that due to the nature of Gaussian functions, the six d-type Gaussians will combine to form linear combinations which correspond to the traditionally accepted five 3 d -~o and one 3s-AO. [3] Similarly the ten f-type Gaussians will produce seven 4 f -~0 and three ~P -A O .…”

“…Here, to make an efficient use of computer time, one must decide not only the number and types of AO used, but also the most efficient distribution of the AO used to describe the different atoms of the molecule. Previous studies on the inversion barriers of CH; [2] and SH2 [3] have shown that small basis sets and bad distributions can produce both qualitatively and quantitatively erroneous results. Thus in the present study, we have examined the effect of adding and distributing different polarization functions on three isoelectronic hydrides of oxygen (OH-, OH2, and OH:) and three isoelectronic hydrides of sulfur (SH-, SH,, and SH:).…”