Real time mixed quantum-classical dynamics with ab initio quartic force field: Application to molecular vibrational frequency analysis

An efficient molecular dynamics methodology, which is suitable for analyzing molecular vibrations of molecules with many degrees of freedom, is presented. The framework of the methodology consists of two main elements. First, a mixed quantum-classical dynamics method is utilized to incorporate quantum effects of nuclei. Second, an approximation of potential energy surface is introduced. The theoretical background, stability of the simulation and the correspondence with quantum simulation are discussed. The accuracy of the methodology over ordinary classical dynamics is described with numerical examples as well.