A detailed model of molecular electrical response for bio -organic species
Knowledge of the electrical charge distribution and polarizability of a molecule is essential for the understanding of intermolecular forces. The capability of a substance to be polarized by an electric field is associated with a number of optical properties including dielectric constants, optical rotatory dispersion, Raman scattering, and depolarization of radiation. This study begins by exploring the computational features necessary to accurately describe the polarization response of a molecule in the presence of an electric field. These features include developing an optimal set of functions, a basis set, with the flexibility to adequately describe the polarized charge cloud of a molecule in the presence of an electric field. In addition, the contribution to electrical response properties arising from instantaneous electron-electron repulsions, or correlation effects, are considered. An understanding of basis set effects and correlation effects is essential in developing an efficient and reliable computational scheme for evaluating molecular response properties. From these results, a reliable method for predicting polarizabilities and higher order response properties for a variety of medium-sized organic molecules has been constructed. Model parameters are reported for anisotropic atomic dipole polarizabilities for H, C, N, O, F atoms in different bonding environments. These atomic polarizabilities are additive contributions to the molecular dipole polarizability tensor and to other aspects of the polarization response of molecules. The model is capable of describing the polarization response in molecules of different size, including molecules with conjugated chains. ^
Major Professor: Clifford E. Dykstra, Purdue University.