  Different computational techniques in combination with molecular dynamics
computer simulation are used to to determine the wall-liquid and the
wall-crystal interfacial free energies of a modified Lennard-Jones (LJ) system
in contact with a solid wall. Two different kinds of solid walls are
considered: a flat structureless wall and a structured wall consisting of an
ideal crystal with the particles rigidly attached to fcc lattice sites.
Interfacial free energies are determined by a thermodynamic integration scheme,
the anisotropy of the pressure tensor, the non-equilibrium work method based on
Bennett acceptance criteria, and a method using Cahn's adsorption equations
based on the interfacial thermodynamics of Gibbs. For the flat wall,
interfacial free energies as a function of different densities of the LJ liquid
and as a function of temperature along the coexistence curve are calculated. In
case of a structured wall, the interaction strength between the wall and the LJ
system and the lattice constant of the structured wall are varied. Using the
values of the wall-liquid and wall-crystal interfacial energies along with the
value for the crystal-liquid interfacial free energy determined previously for
the same system by the "cleaving potential method", we obtain the contact angle
as a function of various parameters; in particular the conditions are found
under which partial wetting occurs.
