Molecular-dynamics simulations of the ethanol liquid–vapor interface

Molecular-dynamics computer simulations have been utilized to study the thermodynamic, structural, and dynamical properties of the liquid–vapor interface of ethanol as a function of temperature. Both the ethanol united-atom and the ethanol all-atom optimized potential models for liquid simulations (OPLS) have been investigated. For both potentials, the calculated ethanol surface tensions as a function of temperature and the orientation of ethanol molecules at the liquid–vapor interface are in agreement with the corresponding experimental data. However, given the degree of agreement between the experimental and simulation data, the OPLS all-atom model better represents the types of interactions present at the liquid–vapor interface of ethanol. In addition, for both potentials the self-diffusion constant of ethanol is found to be larger at the surface than in the bulk of the liquid.