title: The oxidation of Al atoms embedded in water clusters: a dynamical study of the relay (Grotthuss-like) mechanism.
abstract: The dynamics of the oxidation of micro-hydrated Al atoms has been studied taking into account the effect of tunneling. Neutral aggregates of the type Al·(H(2)O)(n), n = {1-8} and Al·(H(2)O)(n)·m(H(2)O) have been considered, where Al·(H(2)O)(n) has been treated by density functional theory (DFT) theory and the other m = {52, 56} waters have been represented by an effective fragment potential (EFP). The results indicate that oxidation may take place quite fast by a relay-type mechanism occurring within a ring of water molecules which involves the Al atom, in which a H atom is transferred. The inclusion of water molecules to form the ring from n = 1 to n = 3 tends to reduce the barrier height but results in lower tunneling transmission factors. The "optimal" ring is the one containing three waters; the four-water one produces lower rates. Coordination of additional waters to Al forming a second ring does not appear to have a further catalytic effect. The inclusion of many additional waters as EFPs, to simulate larger aggregates, increases the rates significantly. The extrapolation to bulk conditions and the possible impact of ionic mechanisms have also been discussed.
authors: Departamento de Química Física, Facultad de Química, Universidade de Vigo, Vigo (Pontevedra), Spain.
authors: S
authors: S
authors: Alvarez-Barcia
authors: J R
authors: JR
authors: Flores