Anisotropic atom displacement in Pd nanocubes resolved by molecular dynamics simulations supported by x-ray diffraction imaging

Nearly identical Pd nanocubes yield an x-ray powder diffraction pattern with interference fringes affording access to unprecedented structural details of nanocrystal size, shape, and complex atomic displacement for a billion-sized population. The excellent agreement between diffraction data and molecular dynamics (MD) provides strong experimental validation of MD simulations and the proposed data-interpretation paradigm. These results show that individual atomic displacements within the nanocubes are not only a function of disrupted bonds and the crystallographic plane of the adjacent surface, but are complex strain gradients extending across all surfaces of the particle strongly influenced by atomic displacements. This observation of nonuniform surface strain and the manner in which it is affected by different sizes, shapes, and locations within each facet could be the key to understanding many surface related properties of shaped nanocrystals including those associated with important catalysis applications.