Molecular dynamics investigation of the inter- and intramolecular motions in liquid methanol and methanol-water mixtures

Molecular dynamics computer simulations were performed at room temperature and selected density on pure liquid methanol and water, and on methanol-water mixtures with methanol mole fractions of 0·1, 0·25 and 0·9. Three-site flexible models were employed both for the methanol and for the water molecules. The inter- and intramolecular motions are analysed in terms of autocorrelation functions and of their Fourier transforms. The translational self-diffusion coefficients correlate well with the available experimental data. The librational and vibrational motions are studied separately for hydrogen-bonded and nonbonded methanol molecules. A correlation between the bonding situation and the vibrational and librational motions of a methanol molecule is demonstrated.