Atomistic Insights into Alkane/Water Interfaces: A Molecular Dynamics Study

The properties of n-alkanes and their interaction with water are of great interest in the chemical and oil industries, where accurate prediction of their thermophysical and interfacial properties is crucial for applications such as enhanced oil recovery and surfactant design. In this work, molecular dynamics simulations of n-pentane, n-hexane, n-cyclopentane, n-cyclohexane, n-heptane, and n-dodecane were conducted to investigate their bulk and alkane/water interfacial properties using the OPLS-AA force field and the TIP3P water model. The computed bulk thermodynamic and dynamic properties including heat capacity, heat of vaporization, isothermal compressibility, diffusion, and viscosity coefficients around ambient temperature and pressure were consistent with the reported data. Molecular structural information at the alkane/water interface was obtained and compared with interfacial thermodynamic properties. Further insights were gained by performing potential of mean force (PMF) calculations to quantify the adsorption energy of alkanes at the alkane/water interface; as expected, a clear dependence on chain length was observed. This study presents a systematic MD analysis combining bulk and interfacial thermodynamics with PMF characterization for both linear and cyclic alkanes.