Free energy of steps at faceted (111) solid-liquid interfaces in the Si-Al system calculated using capillary fluctuation method

Molecular-dynamics simulations using interatomic potentials of the angular embedded atom method form have been performed on the Al-Si system to compute the excess free energy of steps on the (111) solid-liquid interface. The solid-liquid step free energy was obtained by monitoring equilibrium fluctuations in the step position for Si solids in contact with Al-Si liquids of compositions Al-87.4at.%Si and Al-59.4at.%Si at two step orientations, [ 1 1 2 ¯ ] and [ 1 ¯ 1 0 ] . No anisotropy in the step free energy was observed for these two alloying systems, and also, the step free energy for the high concentration and high temperature 87%Si alloy was found to be greater than that of the Al-59.4% alloy. For the low temperature case of Al-30at.%Si the capillary fluctuation method can no longer be applied to extract the step free energy due to smoothness of the steps.