HYDROGEN-BONDING IN LIQUID METHANOL

Molecular-dynamics simulations of liquid methanol have been carried out at two temperatures (T = 300 and 200 K) to investigate the dynamics of hydrogen bonding. The mean lifetime of hydrogen bonds (defined in terms of a time-averaged pair energy) is calculated and found to be 5-7 ps at 300 K, through the results depend on the averaging time used in the hydrogen bond definition. At 200 K the lifetime becomes much longer, by one order of magnitude or more. A bonding state is defined for each molecule according to the number of hydrogen bonds, and the mean lifetime of the states and the rate constants of transition between states are calculated. Molecules with two hydrogen bonds have much longer lifetimes than expected from the assumption that forming and breaking of hydrogen bonds occur randomly. Bonding autocorrelation and state autocorrelation functions are calculated, which enable us to have another definition of lifetimes and to discuss the way in which local diffusion occurs near molecules. © 1990 American Institute of Physics.