MATHEON-ICM WORKSHOP on Free Boundaries and Materials Modeling - Abstract
Krukowski, Stanisław
Growth of crystals encompasses several distinctive processes: diffusive/convective transport of mass and conduction/convection heat transfer, surface reactions and diffusion, adsorption and desorption, and the incorporation into the crystal lattice at kink sites. These processes could have utterly different characteristics. The atomistic processes on GaN(0001) surface were modeled using SIESTA quantum mechanical density functional theory (QM DFT) code. The process of adsorption of various species was analyzed. The process was simulated using Born-Oppenheimer approximation for Cl atom. Both Ga-rich and N-rich surface state was considered. The hydrogen presence was assumed. Surface diffusion was treated using simplified 2-d lattice model. It was shown that the transition between compact, i.e. crystal and open, i.e. fractal shapes results form interplay of the chaotic impact of volume diffusion and ordering influence of surface diffusion processes. These processes could be coupled to volume transport processes. These coupling could lead to numerous instabilities of Mullins-Sekerka type, such as instability of planar surface or circular nucleus, or edge and lacunar instability. These instabilities are characterized by existence of critical length scales. This is joint work with Paweł Kempisty and Paweł Strak (Faculty of Physics, Warsaw University of Technology, 00-672 Warsaw, Koszykowa 75, Poland )