Hexalithiobenzene: A molecule with exceptionally high second hyperpolarizability
Abstract
The electronic structure of the fully lithiated benzene molecule has been calculated at different levels of approximation with particular attention paid to its second hyperpolarizability. It has been estimated that lithiation of the benzene molecule may lead to the enormous increase of the second hyperpolarizability. For hexalithiobenzene the second hyperpolarizability term responsible for the third harmonic generation has been estimated to be of the order of 107e4ao4Eh−3. The reasons for the very large increase of the dipole polarizability, and in particular, of the second hyperpolarizability upon lithiation have been analysed in terms of the electronic structure, orbital energy levels, and the excitation spectrum of the hexalithiobenzene molecule. The main factor responsible for the particularly large values of the studied properties is the electronic valence shell structure of the lithium atom. Although the hexalithiobenzene molecule is used as a model for the study of the lithiation effect, several stable organometallic systems involving alkali metals are known. The present study suggests that among these systems one may find materials of extremly high nonlinear optical efficiency.
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