Burton–Cabrera–Frank spiral growth from screw dislocations
Burton, Cabrera & Frank (1951) showed that crystal growth at low supersaturation occurs via spiral steps emanating from screw dislocations. A dislocation produces a step that winds outward — once a ledge segment longer than the critical radius r* = γΩ/(kT ln(1+σ)) exists, it propagates. The growth rate is parabolic in σ at low supersaturation (v ∝ σ²) and linear at high σ, explaining Arrhenius anomalies seen experimentally.