Surface roughening of normal alkane crystals: Solvent dependent critical behavior

The flat solid-fluid interface undergoes a roughening phase transition at the roughening temperature Tʳ. The step free energy {λ} vanishes at Tʳ, if the temperature T{→}Tʳ. For n-paraffin crystals, the critical behavior of {γ}(T) in the neighborhood of Tʳ is solvent dependent. If n-C₂₅{H}₅₂crystals are grown from n-hexane solutions, the step free energy γ(T) of the 110 faces vanishes discontinuously at{T}ʳ$. In contrast, for n-${C}₂₅H₅₂ crystals grown from toluene solutions {γ}(T) vanishes continuously at Tʳ, showing a Kosterlitz-Thouless type of roughening transition.