The local structure of vartious hydrogen bonded liquids:Vroronoi polyhedra analysis of water, methanol, and HF

摘要

The local structure of three hydrogen bonded liquids compridig clusters of markedly different topolygy:water, methanol, and HF are investigated by analyzing the properties of the Voronoi polyhedra(VP) of the molecules in configurations obtained from Monte Carlo computer simulations. For comparisons, the properties of argon as a nonassociating reference liquid are also sijulations. For comparisons, the properties of argon as a nonassociating reference liquid are also calculated. It is found that in liquid HF the fluctuation of the loacal censity is much larger than in the other three liquids, and hence, besides the dense regions, this liquid contains numerous large voids as well. The size of the largest of these voids is found to be commensurate with a cluster of 11 HF molecules, whereas the number of voids as large as one molecule is in the order of the number of molecules. It is foudn that the number of the hydrogen-bonded neighbors of the HF molecules located at the boundary of such voids does not differ coniderably from that of the other molecules, and thus they do not have any specific topological position(e.g., chain terminal) in the hydrogen bonded chains of the molecules. The shape of the VP is found to reflect the arrangement of the nearest neighbors of the molecules .Thus, the VP is found to teflect the arrangement of the nearsest neighbors of the molecules. Thus, the VP are coniderably less spehericla and their topological properties are distributed in a wider range in the associated liquids than in argon. imilarly, in the hydrogen bonded liquids considerably more geometric neighbor are found than the number of molecules beloning to the first coordination shell. On the other hand, in liquid argon, whioch i a closely packed system, the two values are found to be close to each other. The inhomogeneities of the local density of liquid HF are also reflected in the shape of the VP. The molecules located at the boundary of the large voids are found to have more sphericla VP with more and larger faces than the other ones