Molecular dynamics study of the liquid-vapor interface of lithium bromide aqueous solutions

The molecular dynamics simulations of the liquid-vapor interface of LiBr aqueous solutions were carried out to investigate the structural and thermophysical properties. As concerns the structural properties, the results of molecular dynamics simulation show that the ions exist in the liquid apart from the surface and this tendency becomes strong as the solute concentration is lowered. This phenomenon is due to the desorption of ion. The calculated values such as density or surface tension agree with experimental ones. As concerns thermophysical properties, the number of water molecules in the bulk gas decreases with an increase of the solute concentration. This result represents the depression of vapor pressure. In addition, in order to investigate the dynamic process of water vapor absorption into LiBr aqueous solution, the molecular dynamics simulation under non-equilibrium condition was carried out. The results show that when the solute concentration is low and the temperature is also low, almost all incident water molecules become trapped at the solution surface and then easily diffuse into the bulk liquid, and when the solute concentration is high and temperature is also high, most incident water molecules become trapped at the solution surface, and the sequent processes are very complicated.