Simulation and modeling of the powder diffraction pattern from nanoparticles

While much of current scientific research is focused on how physical properties of nanoparticles – like strength and thermal transport – are dramatically different from their bulk form, their structural differences are also beginning to be understood in terms of diffraction. It is becoming evident that the theories and assumptions used to model the diffraction pattern line profiles from bulk materials are not always appropriate for nanoparticles. For example, the stable atomic structure of multiple twinned nanoparticles, which are composed of intersecting twin planes in a noncrystallographic symmetry, does not have an analog in bulk materials. Also, the large fraction of atoms near the surface requires the consideration of surface effects, which are commonly ignored for bulk materials. The task at hand is then to develop reliable structural models for nanoparticles, and use them to study the features imposed on their powder diffraction line profiles. Atomistic simulations like molecular dynamics have shown to be a powerful tool to simulate the atomic structure and dynamics of materials, and can be coupled with the Debye function to generate the powder diffraction pattern. The purpose of this talk will then be to outline this approach, and use it to study the diffraction pattern from realistic atomic constructions of metallic nanoparticles.