Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5417119 | Journal of Molecular Structure: THEOCHEM | 2009 | 7 Pages |
Abstract
Hatree-Fock calculations at ab initio and semiempirical levels were carried out for the averaged polarizability ãαã and second hyperpolarizability ãγã of two pairs of quadrupolar isomers with different donor and acceptor groups. These properties were correlated with the antibonding/bonding Ï occupation number (Ïâ/Ï ratio). It was found that isomers with extended Ï systems had low Ïâ/Ï ratios and high ãαã and ãγã values, while low ãαã and ãγã values were obtained for isomers with large Ïâ/Ï ratios and no extended Ï system. The PM3 and PM6 ãαã values were found to be in excellent agreement with the HF/6-31+G(d,p) ones. The PM3 values for ãγã were significantly larger than those calculated by HF/6-31+G(d,p), with an average PM3/HF ratio of 1.43. The PM6 results were noticeably better with a ratio of 0.85. The calculation of ãαã and ãγã at MP2/6-31+G(d,p) level for representative isomers showed that the contribution of the electron correlation to their values was small and that the HF/6-31+G(d,p) method provides reliable values at much lower computational cost.
Keywords
Related Topics
Physical Sciences and Engineering
Chemistry
Physical and Theoretical Chemistry
Authors
Emildo Marcano, Emilio Squitieri, Juan Murgich, Humberto Soscún,