Topology versus temperature:: Thermal behavior of H+(H2O)8 and H+(H2O)16

Monte Carlo simulations based on the OSS2 potential indicate the structure of the small protonated water clusters, H+(H2O)(8) and H+(H2O)(16), is far from what could be expected for the proton solvated in bulk water. Near room temperature we find H+(H2O)(n), n=8,16 clusters have a treelike topology with chains of waters emanating from a central H3O+ moiety. Only at lower temperatures do cycles and cages of water appear. These findings bear upon experiments in a variety of disciplines. (C) 2000 American Institute of Physics. [S0021-9606(00)50902-7].