Structure of grain boundaries in nanostructured powders: a Monte-Carlo/EAM numerical investigation

A new approach based on the Embedded Atom Method is applied to model the structure of grain boundaries in nanostructured powders. We choose a set of EAM parameters reproducing bcc as well as fcc structures. A Monte-Carlo scheme, namely various modifications of the well established simulated annealing/Metropolis algorithm, is used to obtain realistic structures of twisted and tilted double and triple grain boundaries as a function of the relative disorientation of the grains. We devise a completely general way to take into account the structure of the grains far from the interface as well as to constraint the relative orientation of the grains, without using periodic boundaries conditions, which would restrict the simulation to certain relative twist or tilt angles for the grains. A few parameters having to be assumed, we compare two methods to model the structure of the grain boundaries. As these two methods, depending on different parameters, lead to similar results, we therefore reduce the number of parameters to be assumed. Results indicate a new configuration which is closer to the bcc structure than the fcc one in the case of iron nanopowders. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2005