Computer simulation study of HNO3 dissociation in aqueous clusters

Hybrid quantum-classical molecular-dynamics simulations were performed for the dissociation process of HNO3 in aqueous clusters containing up to n = 1 24 water molecules. By circumscribing the HNO3 and one water molecule withi n the quantum region, no dissociation was observed, even for the largest cl uster considered, in which the process is expected to be spontaneous. Incor poration of two additional water molecules into the quantum sub-system was necessary to observe the proton transfer. Ionic dissociation takes place fo r n=124 and n=10, but not for the n=3 case, confirming that the threshold c luster size for dissociation is intermediate between the last two values. ( C) 2000 Elsevier Science B.V. All rights reserved.