The velocity source concept

Traditional kinematic wave theory neglects considerations involving free en ergy of a surface and nucleation at the boundary of a surface. As a consequ ence, strictly speaking this theory is only applicable to freely floating p erfect crystals, and when applied to more complex situations the conclusion s may be false. In this paper we argue that boundary conditions, to be take n into account at interface junctions, affect the shape of the crystal. The effect is either microscopic or macroscopic. In the first case, we have a "kinetic meniscus", a curved transition of the size of the critical radius. In the second case, the growth rate is affected macroscopically and we may consider the boundary as a "velocity source" for the affected interface. T hese concepts are essential elements in a version of kinematic wave theory that is applicable to all physically relevant situations. (C) 1999 Elsevier Science B.V. All rights reserved.