STRUCTURE IN LIQUID METHANOL FROM SPATIAL-DISTRIBUTION FUNCTIONS

A structural approach that employs the spatial distribution functions of atoms has been shown recently [J. Chem. Phys. 99, 3049 (1993)] to greatly improve our understanding of the local structure in liquid water. In the present study we obtain the oxygen-oxygen and oxygen-carbon spatial distribution functions, g(OO)(r,OMEGA) and g(OC)(r,OMEGA), respectively, for liquid methanol and use them to characterize its equilibrium structure. For this purpose molecular dynamics simulations with the three-site model of Haughney, Ferrario, and McDonald are carried out at a temperature of 25-degrees-C. Using the spatial distribution functions we demonstrate that the dominant H-bonded structure in this liquid is an open, nonlinear (''zig-zag'') chain of monomers packed spatially in a tetrahedral manner. g(OO)(r,OMEGA) yields an average coordination number of 1.92 which agrees well with results from chain length analysis. There is no evidence in our structural data to support a local planar assembly of oxygen sites. We also observe features in g(OO)(r, OMEGA) which suggest that neighboring H-bonded chains in liquid methanol have a tendency for parallel arrangements.