Abstract :
A method for introducing an effective coordinate for the solvation shell in a hydrogen-bonded cluster with the A–H…B reaction complex is presented. Due to the formation of additional hydrogen bonds between the A–H…B complex and the molecules of the solvation shell proton transfer (PT) is able to occur. An effective coordinate y is introduced which is approximately Jacobian. It is called upon to imitate the action of additional H-bonds which allow for the thermodynamical possibility of PT. To illustrate this method a model three-dimensional potential energy surface (PES), included explicitly the O–H and O…N stretching modes and y, was extracted from an ab initio surface. The PES was calculated for a cluster containing an phenol-ammonia complex surrounded by an ammonia shell (NH3)4. The two lowest proton adiabatic terms were computed. Two possible approaches for treating PT dynamics in the two-level approximation are discussed.
