Incomplete symmetry breaking and anomolous crystallization kinetics at close-packed crystal-liquid interfaces

Stacking faults in close-packed planes are commonly, observed during crystallization. In this paper we demonstrate that this behavior can be described in terms of a simple theoretical description of cr crystallization kinetics that couples two structural order parameters. Wt: establish that the packing degeneracy that permits such faults also fives rise to a striking kinetic effect. The close-packed surface can freeze only when the symmetry of the two possible in-layer packings is broken. either bq fluctuations or longer-range interactions. In the absence of long-range interactions growth can table place only once the supercooling exceeds a critical depinning value associated with a second-order phase transition in a single surface layer.