a1 Division of Applied Sciences, Harvard University, Cambridge, Massachusetts 02138
a2 Solid State Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
An atomistic model for the dependence on interface orientation and velocity v of the solute partition coefficient k during rapid solidification is developed in detail. Starting with a simple stepwise growth model, the simple continuous growth model result is obtained for k(v) when the growth steps are assumed to pass at random intervals rather than periodically. The model is applied to rapid solidification of silicon. Crystal growth at all orientations is assumed to occur by the rapid lateral passage of (111) steps at speeds determined by the interface velocity and orientation. Solute escape is parametrized by a diffusion coefficient at the edge of the moving step and a diffusion coefficient at the terrace, far from the step edge. The model results in an excellent fit to data for the velocity and orientation dependence of k of Bi in Si.
(Received January 30 1987)
(Accepted April 08 1987)
p1 Permanent address: Division of Applied Sciences, Harvard University, Cambridge, Massachusetts 02138.