Effect of the relative orientation of the CN moieties on the static electric (hyper)polarizability of (CN) 2.

We report static electric (hyper)polarizability values of the three linear isomers of (CN) 2 . Large, flexible basis sets have been especially designed for all three molecules and the electric properties have been obtained from finite-field Møller-Plesset perturbation theory and coupled cluster calculations. All three molecules are characterized by large polarizability anisotropies. Self-consistent field calculations of near-Hartree-Fock quality yield the following mean polarizabilities: for CN-NC, 32.42 for NC-CN and 33.46 for CN-CN. For the second hyperpolarizability we obtain for CN-NC, 3090 for NC-CN and 3748 for CN-CN. Thus, electric (hyper)polarizability increases in the order NC-CN<CN-CN<CN-NC at the Hartree-Fock level of theory. Electron correlation does not modify this order. Our final estimates suggest that the relative orientation of the two CN moieties in CN-NC produces the most pronounced nonlinear polarizability effect. [ABSTRACT FROM AUTHOR]