No abstract

Vibrational contributions to the dipole polarizabilities and hyperpolarizabilities of cyclopropenone and cyclopropenethione are reported. Simultaneous calculations have been carried out for the respective saturated and noncyclic counterparts of these molecules. The results have been analyzed and interpreted in terms of different structural and electronic features of the studied molecules: i.e., the oxygen–sulfur replacement, the saturation of the carbon ring, and the removal of the intramolecular strain. For static dipole polarizabilities the vibrational contribution computed at the molecular equilibrium geometry can account for more than 10% of the total value for a given component of the tensor. Both the zero-point vibrational average and pure vibrational terms are important for most of the studied molecules. In the case of the first dipole hyperpolarizability the total vibrational correction is dominated by the pure vibrational term. The vibrational corrections to dipole polarizabilities show certain regularities which can be interpreted in terms of the electronic structure of the investigated molecules. Much less clear is the pattern of behavior for the first dipole hyperpolarizability. It has been found, however, that the analysis of these data is greatly facilitated by the separate consideration of the nuclear relaxation and curvature terms. Limited study of the frequency dependence of the calculated vibrational corrections shows that in the case of the dipole polarizability, they are almost quenched to zero. In contrast, at nonzero frequencies, the vibrational contribution to the first dipole hyperpolarizability tensor β(−ω;ω,0), which determines the so-called electro-optic Pockels effect, can be as important as the pure electronic term.

Articles you may be interested inHow large is the static electric (hyper)polarizability anisotropy in HXeI?The results of ab initio calculations of static electric properties of a series of cyclic conjugated ketones and thioketones are presented. Dipole moments, dipole polarizabilities, as well as the first and second hyperpolarizabilities, were evaluated at different levels of theory: SCF, CASSCF, MP2, CCSD, CCSD͑T͒, and CASPT2 methods were used. Both MP2 and CASPT2 methods have been shown to perform well in the calculation of such properties. The dependence of the electric properties on the extent of the -electron conjugation and on the replacement of the keto by the thioketo group is analyzed. Cyclic conjugated thioketones are shown to exhibit significant nonlinear electric properties which make them prospective building blocks for nonlinear optical materials.