MOLECULAR POLARIZABILITY AND POLARIZABILITY DERIVATIVES IN CYCLOHEXANE ANALYZED WITH THE THEORY OF ATOMS IN MOLECULES

The molecular polarizability of cyclohexane is obtained in an ab initi o calculation with the D95* basis set. The derivatives of the molecul ar polarizability with respect to the symmetric stretch of the axial a nd the equatorial CH bonds are obtained by numerical difference, Wave functions from the molecular orbital calculations are analyzed with th e theory of atoms in molecules, to reveal the relocation of charge den sity which occurs when the molecule is placed in an electric field, at the equilibrium geometry and with the bonds stretched. The molecular polarizability arises from the combined effects of transfer of charge between hydrogen atoms on opposite sides of the molecule and the reori entation of charge around individual atoms (primarily the carbon atom atomic dipoles). Both interatomic charge transfer and intraatomic char ge reorientation are affected by the stretching vibration. The calcula ted results are compared to experimental measurements of molecular pol arizability and polarizability derivatives from Rayleigh and Raman sca ttering. The present method of analysis is compared to other models. P roblems associated with the bond polarizability model, frequently used for the interpretation of Raman scattering intensities, are identifie d.