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

Thu 811:10-14:00P7.31Thickness and compressibility on free and adsorbedliquid filmsEva M. Fernandez, 1 Enrique Chacon, 1 and Pedro Tarazona 21 Instituto de Ciencia de Materiales de Madrid, CSIC, Sor Juan Ines de la Cruz, 28049,Madrid, Spain2 Departamento de Fisica Teorica de la Materia Condensada, UAM, Madrid, SpainInterfacial phenomena as adsorption, wetting, pre-wetting of thin films over solid substrate, thatare results of the interaction between the fluid and the solid substrate, are present both in the natureand in the industry and play an important role in catalysis, biology . . . . A problem of any computeror experimental study of the width of a slab adsorbed is the thermal capillary wave (CW) at theliquid-vapor interface that hidden a sharp view of the interfacial structure. The capillary wavetheory (CWT) provides the framework to analyze surface fluctuations. CWT postulates that thereis an instantaneous surface between the liquid and the vapor called intrinsic surface (IS). In the lastyears two of us proposed a method to calculate the IS called Intrinsic Surface Method (ISM) [1].The ISM allows calculate with very accurate the mean position of the liquid-vapor surface andthe width of the slab without the blurring effects of the CW. In this work we have applied theISM to study the width of a free liquid slab at coexistence and the thickness of an adsorbed filmover a planar wall in a total wetting situation. In order to interpret our results we developed asimple model that includes the effect of the compressibility and evaporation-condensation ofparticles between the liquid and the vapor and which describes the behavior of film thickness andits dispersion for both systems. For a NVT simulation we found that the compressibility and theevaporation-condensation of particles play an essential role to describe the fluctuations of thefilm thickness at the free and adsorbed slab. For the adsorbed slab we found that the effectivepotential is only relevant for thin films due to its short range. Finally, our results suggest that alocal description of the effective Hamiltonian is enough to describe the behavior of our system,although a more systematic studied is necessary.[1] E. Chacón, P. Tarazona, Phys. Rev. Lett. 91, 166103 (2003).31