Surface critical behavior of fluids: Lennard-Jones fluid near a weakly attractive substrate
Physical Chemistry, Dortmund University, 44221 Dortmund, Germany
Published online: 28 April 2005
The phase behavior of fluids near weakly attractive substrates is studied by computer simulations of the coexistence curve of a Lennard-Jones (LJ) fluid confined in a slitlike pore. The temperature dependence of the density profiles of the LJ fluid was used to study the surface critical behavior. A universal critical behavior of the local order parameter, defined as the difference between the local densities of the coexisting liquid and vapor phases at some distance from the pore walls, , is observed in a wide temperature range and found to be consistent with the surface critical behavior of the Ising model. Near the surface the dependence of the order parameter on the reduced temperature obeys a scaling law ~ with a critical exponent of about 0.8, corresponding to the surface transition. A crossover from bulk-like to surface-like critical behavior occurs, when the distance to the surface is about twice the correlation length at the given temperature. Relations between the and transitions in Ising systems and the surface critical behavior of fluids are discussed.
PACS: 05.70.Jk – Critical point phenomena / 64.60.Fr – Equilibrium properties near critical points, critical exponents / 64.70.Fx – Liquid-vapor transitions
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2005