Just another WordPress site - Ruhr-Universität Bochum

The atomistic simulation of polycrystalline growth with an empirical potential requires an accurate modeling of the atomic configurations at grain boundaries. We refine an existing embedded-atom potential for bulk titanium to reproduce systems with small atomic coordination, namely, clusters of up to nine atoms, the relaxation of the (0001) surface and the adatom diffusion on this surface. We find that simulating Ti growth can be limited to the (0001) surface and the rather small class of grain boundaries with angles of coincidence-site lattices. We determine the atomic structure of the Ti(0001) Sigma=7 grain boundary with molecular statics and find exclusively pentagonal elementary structural units. The potential energy surface shows that this grain boundary imposes a massive barrier on surface diffusion. We use the elementary cells of the coincidence-site lattice to construct two periodic systems with grain boundaries: an isolated grain within an environment of different crystalline orientation and two antiparallel grain boundaries. Molecular dynamic simulations show that this isolated grain is not stable and that the growth evolution of the system with two antiparallel grain boundaries depends strongly on the angle of incidence.