Extracting vibrational anharmonicities from short driven molecular dynamics trajectories

Abstract

Anharmonicities provide a wealth of information about the vibrational dynamics, mode coupling and energy transfer within a polyatomic system. In this contribution, we show how driven molecular dynamics trajectories can be used to extract anharmonicity properties under very short times of a few hundreds of vibrational periods, using two exciting fields at- and slightly off-resonance. Detailed analyses on generic quartic potential energy surfaces and applications to various model systems are presented, giving good agreement with perturbation theory. Application to a realistic molecule, cubane (C $$_8$$ H $$_8$$ ), modelled with a tight-binding quantum force field, further indicates how the method can be applied in practical cases.