Relation between hydrogen bonding and intramolecular motions in liquid and supercritical methanol

Molecular dynamics (MD) simulations of liquid and supercritical methanol have been performed using a well known flexible 3-sites model. The analysis of the hydrogen bond network has been carried out using first standard geometric criteria on dimers. We then analyzed the effect of hydrogen bonds on single-molecule properties by studying the vibrational and librational motions of a molecule in terms of specific antocorrelation functions and their Fourier transforms. This approach led to an alternative definition of the hydrogen bond, based on molecular properties that can be compared directly with results from molecular spectroscopies (infrared and Raman). It is found that geometric and "spectroscopic" criteria lead to consistent average results over a wide range of thermodynamics conditions while individual molecular results can be different. (C) 2006 Elsevier B.V. All rights reserved.