Steps on surfaces in modeling crystal growth
Deij, M. A., Cuppen, H. M., Meekes, H., Vlieg, E.
CRYSTAL GROWTH & DESIGN 7 (10): 1936-1942 OCT 2007
      
Abstract: When modeling crystal growth and crystal morphology, steps on surfaces are important for the correct description of the phenomena taking place. Morphology prediction, however, has been dominated by the Hartman-Perdok theory of periodic bond chains (PBCs), connected nets, and attachment energy, where steps are ignored. In this paper, using three model systems we show that the Hartman-Perdok theory breaks down for complex connected net topologies, in terms of connected nets having a roughening temperature equal to zero. A two-fold solution to understanding this anomalous behavior is presented. First of all, looking at step structures that can form on a connected net orientation and calculating the energies associated with them lead to a better understanding of the roughening behavior. A recently developed algorithm for that, called STEPLIFT, is introduced in the accompanying article in this issue (Cryst. Growth Des. 2007, 7, 1949-1957). Second, performing atomistic Monte Carlo simulations for selected orientations allows for the detailed simulation of the growth process as a function of the driving force. The presence or absence of a nucleation barrier can thus be tested. These two complementary methods give new insights in the possible growth behavior and roughening of complex organic materials and are expected to lead to new methods for modeling crystal growth, crystal surfaces, and crystal morphology.