Molecular dynamics study on the vibrational energy relaxation of O-D stretch of HOD in liquid H2O

Vibrational energy relaxation of O-D stretch of HOD in liquid H2O at 300 K is studied with molecular dynamics simulation based on the Fermi's golden rule. The Fourier transform of the force force time correlation function along the O-D stretch obtained from the simulation is used to calculate the relaxation time. Both rigid and flexible solvents are applied to reveal the relaxation mechanism. We find that the relaxation time of O-D stretch fundamental is 19.05 ps for the rigid solvent and 5.04 ps for the flexible solvent which is comparable to the experimental value 1.45 ps. The main pathway of O-D stretch fundamental is transition to the bend fundamental for the rigid solvent and direct relaxation to the ground state when solvent vibrations are included.