A MOLECULAR-DYNAMICS STUDY OF THE HEXANE WATER INTERFACE

A molecular dynamics simulation of the interface between liquid hexane and liquid water has been performed. The sample consisted of a two-phase system comprising 187 hexanes and 1200 waters, confined to a box measuring 83.19 × 30.1 × 30.1 Å3. A total of 94.4 ps was simulated (60 ps of equilibration and 34.4 ps of analysis). The interface was found to be about 10 Å wide. It does not appear to be molecularly sharp. A small number of hexane molecules are detached, i.e., completely surrounded by water. This is inconsistent with the known solubility of hexane in water and is believed to be an artifact of the intermolecular potentials used. Differences between the interfacial and bulk liquids were observed. Water is more structured in the interfacial region than in bulk, and hexane molecules in the interfacial region were found to exhibit an excess of trans conformations relative to bulk. Neither component displays any preferential orientation with respect to the lab frame. © 1990 American Chemical Society.