Path integral molecular dynamic study of nuclear quantum effect on small chloride water clusters of Cl-(H2O)1-4

The nuclear quantum effect, which plays important roles on ionic hydrogen bonded structures of Cl-(H2O)(n) (n = 1-4) clusters, was explored by carrying out path integral molecular dynamic simulations. An outer shell coordinate r(l)(Cl center dot center dot center dot O) is selected to display the rearrangement of single and multi hydration shell cluster structures. By incorporating the nuclear quantum effect, it is shown that the probability for single shell structures is decreased while the probability for multi shell structures is increased. On the other hand, the correlations between changing of bonded H* atom to Cl- (defined as delta) and other cluster vibration coordinates are studied. We have found that delta strongly correlates with proton transfer motion while it has little correlation with ion-water stretching motion. Contrary to theta(H-O-H*) coordinate, the correlations between delta and other coordinates are decreased by inclusion of nuclear quantum effect. The results indicate that the water-water hydrogen bond interactions are encouraged by quantum simulations. (C) 2013 Elsevier B. V. All rights reserved.