Page 296 - Strategies and Applications in Quantum Chemistry From Molecular Astrophysics to Molecular Engineer

Coupled Hartree-Fock Approach to Electric Hyperpolarizability Tensors
in Benzene

P. LAZZERETTI, M. MALAGOLI and R. ZANASI
Università di Modena, Dipartimento di Chimica, via G. Campi 183, 41100 Modena,
Italy

1. Introduction

In the presence of a static, spatially uniform electric field the electronic cloud of
atomic and molecular systems gets polarized. The energy, W, can be written as a
Taylor series [1–3]

where is the unperturbed energy, is the permanent electric dipole moment
and the coefficients etc. are known as (static) electric polarizabilities.
Non-linear response of the system is rationalized via hyperpolarizabilities
(sum over repeated Greek indices is implied), etc.. The total electric dipole moment
of the molecule in the presence of the electric field is [1–3]

According to (1) and (2), the response tensors are defined

279
Y. Ellinger and M. Defranceschi (eds.), Strategies and Applications in Quantum Chemistry, 279–296.
© 1996 Kluwer Academic Publishers. Printed in the Netherlands.