Optimization of width parameters for quantum dynamics with frozen Gaussian basis sets

Frozen Gaussian wavepackets for simulations of molecular dynamics including quantum effects require specification of the widths of the complex Gaussian functions, which may be viewed as parameters. Motivated by the standardized basis sets used in electronic structure theory, we develop a scheme for optimizing the width parameters for frozen Gaussian nuclear basis functions. The optimization approach maximizes the overlap between a reference ground state vibrational wavefunction in internal coordinates and a wavefunction determined by the product of complex Gaussians in Cartesian coordinates. After optimizing the parameters using a test set of over 100 molecules, the average width parameters are determined for a set of common atoms (H, C, O, N, F, S and Cl). The parameters are tested for excited state dynamics of ethylene and benzene using the ab initio multiple spawning (AIMS) method.