TOPOLOGICAL AND SPATIAL STRUCTURE IN THE LIQUID-WATER-ACETONITRILE MIXTURE

We have studied the structure of the liquid-water-acetonitrile mixture using molecular configurations obtained by molecular dynamics simulat ion. Spatial distribution functions have been used to analyze the loca l structures surrounding the molecules. The effective hydrogen-bond de finition has been used to study basic hydrogen-bond properties and top ological properties of the hydrogen-bond network. The topology of the network depends on the acetonitrile concentration. Up to a critical co ncentration, there is an infinite network of hydrogen-bonded water mol ecules. At higher concentrations, the network cannot be supported, and finite water clusters form. In order to characterize the networks and clusters, we have calculated some properties of loops and chains of w ater molecules. The patterns of hydrogen bonds surrounding the molecul es and the size distribution of the clusters have also been calculated . We suggest that this approach can be useful when studying the struct ure of other liquid mixtures where hydrogen bonds are an important mod e of interaction. [S1063-651X(98)04510-3].