Stable  long-time  semiclassical description of zero-point energy in  high-dimensional molecular  systems

Vitaly Rassolov, Department of Chemistry, University of South Carolina

Classical   molecular dynamics provides a reasonable general picture of chemical reaction dynamics in most systems of practical interest.  However, comparison of typical reaction energies and zero-point energy show that quantum mechanical effects play an important role in many systems, particularly for reactions of proton transfer. The adequate theoretical description of quantum effects is proved to be a very challenging task, to large extend due to lack of theoretical method that works for anharmonic high dimensional systems for a time longer than few oscillation periods.  We present such a method. It is based on a  numerically cheap  linearized quantum force approach;  stabilizing  terms compensating  for the linearization errors are added into the time evolution equations for the classical and nonclassical components of the momentum operator. The  wavefunction normalization  and energy are rigorously conserved.  Numerical tests are performed for model systems of up to 40 anharmonic degrees of freedom.

Oral