Instantaneous normal mode analysis of liquid methanol

The instantaneous normal modes for liquid methanol at 200 K are calculated and related to the topologically linear hydrogen bond network in this system. A shoulder observed in the spectra of both collective and single molecule correlation functions is explained as arising from the presence of "stretching" modes of the hydrogen bonded network, similarly to what happens in liquid hydrogen fluoride. In the case of methanol, however, the relation between the chain dynamics and the instantaneous normal modes is much less evident, due to the strongest "coupling" of the chain motion to other diffusive processes present in the liquid. (C) 2001 American Institute of Physics.