Resolution of a long-standing problem in elemental sulfur chemistry: a theoretical study of tetrasulfur

• Published in: Journal of the American Chemical Society Vol. 112; no. 24; pp. 8719 - 8733
• Main Authors: Quelch, Geoffrey E, Schaefer, Henry F, Marsden, Colin J
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 01.11.1990
• Subjects: 400201 - Chemical & Physicochemical Properties; DATA; ELECTRONIC STRUCTURE; ELEMENTS; ENERGY; INFORMATION; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ISOMERS; MATHEMATICAL MODELS; NONMETALS; NUMERICAL DATA; POTENTIAL ENERGY; SULFUR; THEORETICAL DATA
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja00180a012

Theoretical studies of the potential energy surface of a poorly understood allotrope of elemental sulfur, S{sub 4}, have been performed with use of ab initio electronic structure theory. Eleven different isomers have been considered. Singlet states have been studied with SCF, two-configuration SCF (TCSCF), CISD (single and double excitation configuration interaction), and TC-CISD levels of theory, and selected triplet states have also been investigated with SCF and CISD theory. A few studies have also been performed on the most stable isomers with MR (multi-reference)-CISD, CCSD (coupled cluster theory with single and double substitution), and CCSDT-1 (CCSD with linearized triple substitutions) methods. Two basis sets, of double-{zeta} plus polarization (DZP) and triple-{zeta} plus double polarization (TZ2P) quality, respectively, have been used.The effects of f-functions on the S-S bond have been investigated with S{sub 2} as an example with a TZ2P+f basis set. Harmonic vibrational frequencies, infrared, and some Raman intensities have been evaluated, as have the ionization energies and the lowest energy electronic transitions for the most stable isomers. Experimental data for these properties are compared with the authors theoretical results.