The diffusional dynamics of liquid methanol. New cross-correlation functions

Abstract

The application of a new rotating frame theory for asymmetric-top diffusion to methanol has produced, via computer simulation, a range of cross-correlation functions with which to measure the fine details of the molecular dynamics. Two of these cross-correlation functions have been examined in this paper together with autocorrelation functions of accelerations such as that of Coriolis which involves simultaneously the linear and angular motion of the molecule. The inertia distribution in the free methanol molecule plays a dominant role in the liquid-state molecular dynamics. For example, the anisotropy of the inertia distribution in methanol causes one element of one of the cross-correlation functions investigated to be a hundred times greater in normalised magnitude than the element corresponding to the axis of the least moment of inertia. This type of cross-correlation function is therefore extremely sensitive to the details of simultaneous rotational and translational diffusion in a hydrogen-bonded liquid such as liquid methanol at 293 K.