Structure in liquid methanol from spatial distribution functions

Abstract

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, gOO(r,Ω) and gOC(r,Ω), 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 °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. gOO(r,Ω) 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 gOO(r, Ω) which suggest that neighboring H-bonded chains in liquid methanol have a tendency for parallel arrangements.