Molecular dynamics study of the temperature dependence of the interfacial thickness in two-dimensional fluid phases

The thickness of the interface between two-dimensional fluid phases is determined as a function of temperature by using the method of molecular dynamics. The model fluid is one of particles interacting via a truncated Lennard-Jones potential. Periodic boundary conditions are used and no macroscopic external field such as gravity is imposed. The temperature is varied between that of the triple point to values as close to the critical point as is consistent with the finiteness of the system studied on the computer. Because of the relatively small interfacial area probed in these simulations, long-wavelength capillary waves are strongly suppressed and within statistical uncertainty, the results for the interfacial thickness are found to be consistent with the prediction of the nonclassical van der Waals theory of the intrinsic interface.