8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P7.30Thu 811:10-14:00On perturbative Monte Carlo methodologies fordetermining the fluid-fluid surface tension - applicationto molecular fluidsBlas Felipe, 1 Luis MacDowell, 2 A. Ignacio Moreno-Ventas Bravo, 1 and FranciscoJosé Martinez Ruiz 11 Universidad de Huelva, Departamento de Fisica Aplicada, Facultad de CienciasExperimentales 21071, Huelva, Spain2 Universidad Complutense, Madrid, SpainIn recent years, Monte Carlo methods for determining fluid-fluid interfacial properties, with particularemphasis on the calculation of surface tension, have experienced a great development in thecomputer simulation community. Particularly, the route for calculating the surface tension basedon its thermodynamic definition is being used by many different groups, and a number of new techniquesand methodologies, including the Test-Area (TA), the Wandering Interface Method (WIM)or the Expanded Ensemble (EE), are currently being used and developed. In this work we use thesemethodologies and examine the interfacial properties of chains formed by up to 16 monomers interactingthrough two different spherically truncated (but not shifted) intermolecular potentials(Lennard-Jones and square-well potentials). Special care is taken in a number of methedologicaltopics, including the election of the intermolecular potential cutoff distance, the calculation of thelong-range corrections to the potential, the determination of the vapour pressure of the systems understudy, and also the estimation of the statistical errors associated to thermodynamic integrationcalculations. For the case of Lennard-Jones chains, we account for the long-range intermolecularinteractions neglected explicitly during the simulation using the appropriate inhomogeneous longrangecorrections. We show that the corrections may be transformed into an effective long-rangepair potential plus a selft term, thus allowing for a fast and easy implementation of the method. Thesurface tension, as well as other interfacial properties, such as density profile, coexistence density,critical temperature and density, vapour pressure, and interfacial width, are obtained as a functionof temperature for different chain lengths. The study of interfacial properties in both models withchain length shows asymptotic increase for the surface tension and realted asymptotic decrease forthe interfacial width.30