A PHASE FIELD APPROACH FOR DIRECT CALCULATION OF INTERFACIAL FREE ENERGY OF SOLID-GAS AND SOLID-LIQUID INTERFACES IN LENNARD-JONES SYSTEMS

. The interfacial free energy -y, (between solid-gas, solid-liquid or liquid-gas interfaces) plays a critical role in many physical and chemical processes involving material surfaces. Due to experimental difficulties in measuring -y various alternative theoretical or computational approaches have been suggested to date. However, despite being commonly used in interface modeling, phase fields models have not been fully exploited for addressing the question of anisotropy in -y. In this work we propose phase field methodologies that use real parameters to directly obtain -y and its anisotropy. The approach is successfully applied to Lennard-Jones system for liquid-gas and solid-gas interfaces. In particular, a novel discrete version of phase field method is introduced for modeling of the solid-gas interfaces of Lennard-Jones systems on the actual fcc lattice. The approach provides a methodology to understand the process of transfer of microscopic anisotropy to the macroscopic scale. Interfacial free energy, -y, is calculated at multiple different conditions (including the triple point) for different orientations. Results show that -y is larger in the [100] direction than [110] direction by several percent. The results are compared with the literature.