New Development of Kramers-Fokker-Planck Equation of Polyatomic Molecules

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How is the dynamics in condensed system recognized? We tried to understand its characteristics from the viewpoint of energy relaxation processes from an HF molecule to its surrounding water solvent system.Since the dynamics in condensed system should be considered on the basis of stochastic theory, observables must be statistically calculated. Therefore, the super-multi concurrent molecular dynamics simulation system was developed.From those simulations of energy relaxation process using the system involved, it is found that solvated water molecules around the vibrationally excited HF molecule requires their internal vibrational modes for energy transfer. Such energy transfer pathway depends on vibrational vector of excitation mode of the HF molecule. It is concluded that intra-molecular vibrational couplings are dominant on the energy relaxation process.In relation to the Kramers-Fokker-Planck equation modeled condensed systems, furthermore, it was investigated to select which coordinates systems could represent molecular dynamics. We considered that time scales of observables should be introduced in correspondence with molecular fluctuation. It was found that the characteristics depend properly on the time window size.