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Ab initio study of cyclic siloxanes (H 2 SiO) n : n = 3, 4, 5
Author(s) -
Kudo Takako,
Hashimoto Fujiko,
Gordon Mark S.
Publication year - 1996
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/(sici)1096-987x(19960715)17:9<1163::aid-jcc9>3.0.co;2-q
Subject(s) - ab initio , homogeneous space , perturbation theory (quantum mechanics) , chemistry , computational chemistry , potential energy surface , maxima and minima , crystallography , physics , geometry , mathematics , organic chemistry , quantum mechanics , mathematical analysis
The geometry optimizations for several conformations of tri‐, tetra‐, and pentacyclosiloxane (H 2 SiO) n ( n = 3, 4, and 5) were carried out, and the relative stabilities were compared at the Hartree‐Fock (HF) and second order perturbation theory (MP2) levels of theory using the 6–31G* and 6–311G( d, p ) basis sets. At the highest levels of theory, the only minimum for n = 4 ( D 4 ) occurs at the highly symmetric D 4 h structure. In contrast, several, nearly isoenergetic, minima are found on the D 5 surface. These have C 1 , C 2 , C s , and D 5 h symmetries. While the C 1 structure has the lowest MP2/6–311G( d, p ) energy, this species is predicted to be highly fluxional, and the distribution of isomers is dependent on temperature. © 1996 by John Wiley & Sons, Inc.