Mixed quantum-classical molecular dynamics study of vibrational relaxation of CN− ion in water: an analysis of coupling as a function of time

Mixed quantum-classical molecular dynamics method has been applied to vibrational relaxation of CN− in water, where coulombic force is predominant in the interaction. The calculation demonstrated that time-dependent interaction between the solute vibrational degree of freedom and the solvent water shows random-noise-like behavior, no collisional or stationary coupling observed in gas or solid, respectively, being found. This is in contrast to the short-ranged-force system where the collision plays a dominant role in the relaxation. The interaction has been analyzed in detail as a function of time defining the effective coupling for the relaxation.