Molecular clusters in liquid methanol:: a Reverse Monte Carlo study

The structure and topology of molecular clusters present in liquid methanol has been investigated by Reverse Monte Carlo (RMC) simulation. In the simulation results of an X-ray and a neutron diffraction experiment, the latter being performed on fully deuterated methanol, has been fitted simultaneously. Due to the weak contribution of the O-H correlation in the fitted functions, the resulting O-H partial pair correlation function is found to be unreliable. In particular, the height of its first peak, which describes the hydrogen bonding in the system, appears to be extremely low. Therefore the structure of the hydrogen bonds has not been analyzed. The analysis of the existing molecular clusters, based on the O-O separation of the molecules, reveals that about 20% of the molecules are monomers, about one third of the clusters contain cyclic unit, and most of the cycles are built up by either three or four molecules. No significant amount of hexameric rings are found. (C) 2000 Elsevier Science B.V. All rights reserved.