Parameters in the model are fixed from experimental measurements near 900 deg C under the assumption that there is local mass transport through surface diffusion and that step motion is limited by the attachment rate of adatoms to step edges. The direct heating current is treated as an external driving force acting on each adatom.
Numerical calculations show both qualitative and quantitative agreement with experiment.
A force in the step down direction will destabilize the uniform step train towards step bunching. The model is extended to include the effect of direct hopping of adatoms between different terraces. These simulations give much better agreement with experiment than previous work. We find a new step bending instability when the driving force is along the step edge direction. This instability causes the formation of step bunches and antisteps that is similar to that observed in experiment.