INVESTIGATION OF THE UNIQUENESS OF THE REVERSE MONTE-CARLO METHOD - STUDIES ON LIQUID WATER

Reverse Monte Carlo (RMC) simulation of liquid water has been performe d on the basis of experimental partial pair correlation functions. The resulted configurations were analyzed in various aspects; the hydroge n bond angle distribution, three body correlation and orientational co rrelation were calculated. The question of the uniqueness of the RMC m ethod was also examined. In order to do this, two conventional compute r simulations of liquid water with different potential models were per formed, and the resulted pair correlation function sets were fitted by RMC simulations. The resulted configurations were then compared to th e original configurations to study how the RMC method can reproduce th e original structure. We showed that the configurations produced by th e RMC method are not uniquely related to the pair correlation function s even if the interactions in the original system were pairwise additi ve. Therefore the difference between the original simulated and the RM C configurations can be a measure of the uncertainty of the RMC result s on real water. We found that RMC produces less ordered structure tha n the original one from various aspects. However, the orientational co rrelations were reproduced rather successfully. The RMC method exagger ates the amount of the close packed patches in the structure, although these patches certainly exist in liquid water. (C) 1996 American Inst itute of Physics.