Does Young's equation hold on the nanoscale? A Monte Carlo test for the binary Lennard-Jones fluid
Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research Jakkur, Bangalore, 560064, India
2 Institut für Physik, Johannes Gutenberg-Universität - Staudinger Weg 7, D55099 Mainz, Germany
Accepted: 13 October 2010
When a phase-separated binary (A+B) mixture is exposed to a wall, that preferentially attracts one of the components, interfaces between A-rich and B-rich domains in general meet the wall making a contact angle θ. Young's equation describes this angle in terms of a balance between the A-B interfacial tension γAB and the surface tensions γwA, γwB between, respectively, the A- and B-rich phases and the wall, γABcos θ = γwA − γwB. By Monte Carlo simulations of bridges, formed by one of the components in a binary Lennard-Jones liquid, connecting the two walls of a nanoscopic slit pore, θ is estimated from the inclination of the interfaces, as a function of the wall-fluid interaction strength. The information on the surface tension difference γwA − γwB are obtained independently from a new thermodynamic integration method, while γAB is found from the finite-size scaling analysis of the concentration distribution function. We show that Young's equation describes the contact angles of the actual nanoscale interfaces for this model rather accurately and the location of the (first-order) wetting transition is estimated.
PACS: 68.08.Bc – Wetting / 05.70.Np – Interface and surface thermodynamics / 64.75.Jk – Phase separation and segregation in nanoscale systems
© EPLA, 2010