Abstract
The RHF/6-31G longitudinal vibrational second hyperpolarizabilities of increasingly longer polyyne chains have been computed within the double harmonic oscillator approximation. Similarly to polyacetylene, the largest contribution comes from the [α2]0,0 term. About 95% of the latter arises from what we call the quasi-ECC mode. It converges rapidly with chain length to an asymptotic limit slightly (7%) smaller than its static electronic counterpart. The [μβ]0,0 term is negligible. The inclusion of electron correlation within the MP2/6-31G scheme leads to a decrease of the γv/γe ratio by a factor going from roughly 3 for the dimer to 2 for the tetramer.
Original language | English |
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Pages (from-to) | 115-122 |
Number of pages | 8 |
Journal | Journal of Molecular Structure: THEOCHEM |
Volume | 425 |
Issue number | 1-2 |
Publication status | Published - 19 Feb 1998 |
Keywords
- Ab initio quantum chemical calculations
- Electronic second hyperpolarizability
- Polyyne chains
- Vibrational second hyperpolarizability