Self-consistent-field lattice gas model for the surface ordering transition of n-hexadecane

It is known from experiments that the solid-liquid phase transition of n-alkanes involves surface freezing. On cooling, a monomolecular surface layer crystallizes first. Upon further cooling, the bulk solidifies. The orientational ordering aspect of n-hexadecane freezing is modeled with a self-consistent-field lattice gas theory, showing that both events are first-order transitions. It is assumed that the CH3 segments are more surface active than the CH2 ones. This initiates at high T a slight orientational bias, but at low T a cooperative alignment of the C-16 perpendicular to the interface.