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Wall-liquid and wall-crystal interfacial free energies via thermodynamic integration: a molecular dynamics simulation study.

Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR), 51170 Köln, Germany.
The Journal of Chemical Physics (Impact Factor: 3.12). 07/2012; 137(4):044707. DOI: 10.1063/1.4738500
Source: PubMed

ABSTRACT A method is proposed to compute the interfacial free energy of a Lennard-Jones system in contact with a structured wall by molecular dynamics simulation. Both the bulk liquid and bulk face-centered-cubic crystal phase along the (111) orientation are considered. Our approach is based on a thermodynamic integration scheme where first the bulk Lennard-Jones system is reversibly transformed to a state where it interacts with a structureless flat wall. In a second step, the flat structureless wall is reversibly transformed into an atomistic wall with crystalline structure. The dependence of the interfacial free energy on various parameters such as the wall potential, the density and orientation of the wall is investigated. The conditions are indicated under which a Lennard-Jones crystal partially wets a flat wall.

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    ABSTRACT: Different computational techniques in combination with molecular dynamics computer simulation are used 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 the 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.
    The Journal of Chemical Physics 08/2013; 139(8):084705. · 3.12 Impact Factor

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