Modeling molecular response in uniform and non-uniform electric fields

Abstract

The response of a molecule to an electric field E, often a model of environment, can be expressed in terms of a sum of power series expansions. We investigate the accuracy and limits of applicability of this expression using one-, two-, and three-dimensional models of the hydrogen-bonded complex, ClH:NH(3). Energetic, structural, and vibrational spectroscopic characteristics are determined at first- and second-order in E and [nabla]E and compared with ab initio values for a range of uniform and non-uniform electric fields chosen to simulate molecular environments. It is found that even at field strengths large enough to cause dramatic structural change in the complex, energetic, structural, and vibrational spectroscopic characteristics are accurately calculated using only terms linear in E and [nabla]E. These results suggest that knowledge of the zero-field molecular potential energy, dipole, and quadrupole moment surfaces may be sufficient to accurately model the interaction of a molecule with a wide range of chemical environments.