Screw Dislocation BCF Mechanism

Burton, Cabrera and Frank have attempted to take into account the effect that occurs at low supersaturation and requires screw dislocations to provide a 

This mechanism occurs at moderate supersaturation and involves two-dimensional surface nucleation on a developing crystal. The theory describes the growth of a layer from a nucleus that exists on a flat surface. The growth rate is roughly proportional to the exponential of the supersaturation  

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For a > 5, a smooth surface is indicated and, as the high energy barrier discourages surface nucleation at low supersaturation, growth generally proceeds by the screw dislocation (BCF) mechanism (equation 6.10) in which case the face growth rate, v, is given by... 

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