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Evolution of polarizabilities and hyperpolarizabilities with molecular aggregation: A model study of acetylene clusters
Author(s) -
Augspurger Joseph D.,
Dykstra Clifford E.
Publication year - 1992
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560430112
Subject(s) - hyperpolarizability , acetylene , polarizability , intermolecular force , chemistry , dimer , ab initio , dipole , chemical physics , computational chemistry , ab initio quantum chemistry methods , molecule , organic chemistry
Ab initio and model calculations on linear clusters of acetylene molecules have been carried out to identify the effect of weak intermolecular interaction on the intrinsic dipole polarizability (‐) and the second hyperpolarizability (γ) and, in particular, to determine the three‐body and higher‐order effects. Ab initio and model calculations on a linear dimer show clearly that the evolution of properties from the separated limit is largely a consequence of the mutual polarization as the monomers begin to interact. This reveals that intermolecular quantum features are not significant. Furthermore, higher‐order response properties play a negligible role in the evolution of lower‐order cluster properties. For instance, the hyperpolarizability γ of the monomer is relatively unimportant in the evolution of α of the dimer; the change in α due to dimer formation is dictated largely by the mutual polarization via the intrinsic α′s of the monomer. With this determination, an electrical interaction model can be used to explore α and γ of long acetylene chains, and this serves as a guide to the vibronic coupling effects on hyperpolarizabilities of longchain species. We find, in particular, that the hyperpolarizability of the subunits of long acetylene chains are dramatically enhanced by intermolecular electrical interaction.