화학공학소재연구정보센터
Journal of Physical Chemistry, Vol.98, No.3, 771-776, 1994
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 initio calculation with the D95** basis set. The derivatives of the molecular polarizability with respect to the symmetric stretch of the axial and the equatorial CH bonds are obtained by numerical difference, Wave functions from the molecular orbital calculations are analyzed with the theory of atoms in molecules, to reveal the relocation of charge density 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 reorientation of charge around individual atoms (primarily the carbon atom atomic dipoles). Both interatomic charge transfer and intraatomic charge reorientation are affected by the stretching vibration. The calculated results are compared to experimental measurements of molecular polarizability and polarizability derivatives from Rayleigh and Raman scattering. The present method of analysis is compared to other models. Problems associated with the bond polarizability model, frequently used for the interpretation of Raman scattering intensities, are identified.