Orientation dependent interface mobilities in a kinetic mean field theory of freezing and melting

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Abstract
The microscopic dynamics of freezing and melting at the 100 and 111 surfaces of a simple cubic crystal are examined. The kinetics are described using coupled Landau–Ginzberg equations based on a mean field approximation of the face centered cubic lattice gas with nearest and next nearest neighbor interactions. Anomalous large structural fluctuations are found at the equilibrium 100 surface, a result of the weak coupling between close packed 100 planes. This feature also gives rise to a large anisotropy in interface mobilities on freezing with the 100 surface mobility vanishing unless fluctuations or longer range interactions are included. The interface mobilities during melting are found to be substantially larger than those found during freezing for both surfaces, a result attributed to the asymmetry between crystal and liquid in the free energy functional.