Bond-Dependent Thole Model for Polarizability and Spectroscopy

We present a new model for the calculation of molecular polarizabilities from effective atomic polarizabilities. This model is based on the Thole modified dipole interaction model for molecular polarizabilities, where the total polarizability is computed as a sum of effective atomic polarizabilities modified by dipole-dipole interactions. We extend this model by making the atomic polarizabilities explicit functions of the interatomic distances, scaling them by the radius of the volume an atom occupies in a molecule. We use the SCAN functional to show that this model, denoted TholeL, yields accurate molecular polarizabilities with little dependence on the training set. We also demonstrate that the TholeL model yields accurate polarizabilities for configurations far from the ground state structure for a wide range of molecules. Finally, we show that the TholeL model can be used to generate accurate Raman spectra for water, crystalline urea, and urea in water from ab initio molecular dynamics simulations.