Atomic structure of nanocrystalline metals studied by diffraction techniques and exafs

The relation between the nanometer-scale structure nod scattering and EXAFS experimental data is discussed on the basis of the atomic density distribution function. The available experimental information is reviewed, with an emphasis on the model substance Pd. Decreasing the grain-size to the nm-scale induces lattice strains and a modified Debye Waller parameter. Immediately after preparation, the grain boundaries are in a non-equilibrium state, which relaxes to a state with higher atomic short-range order upon aging at room temperature. Strong grain-growth at room temperature indicates a high atomic mobility in the grain boundary regions. Small-angle scattering appears to be dominated by porosity for all but the densest available samples.