Surface roughening of normal alkane crystals: Solvent dependent critical behavior.

Abstract

The flat solid-fluid interface undergoes a roughening phase transition at the roughening temperature T r . The step free energy γ vanishes at T r , if the temperature T→T r . For n-paraffin crystals, the critical behavior of γ(T) in the neighborhood of T r is solvent dependent. If n-C 25 H 52 crystals 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 25 H 52 crystals grown from toluene solutions γ(T) vanishes continuously at T r , showing a Kosterlitz-Thouless type of roughening transition