INCOMPLETE SYMMETRY-BREAKING AND ANOMALOUS CRYSTALLIZATION KINETICS AT CLOSE-PACKED CRYSTAL-LIQUID INTERFACES

Stacking faults in close-packed planes are commonly, observed during c rystallization. In this paper we demonstrate that this behavior can be described in terms of a simple theoretical description of cr crystall ization kinetics that couples two structural order parameters. Wt: est ablish that the packing degeneracy that permits such faults also fives rise to a striking kinetic effect. The close-packed surface can freez e only when the symmetry of the two possible in-layer packings is brok en. either bq fluctuations or longer-range interactions. In the absenc e of long-range interactions growth can table place only once the supe rcooling exceeds a critical depinning value associated with a second-o rder phase transition in a single surface layer.