Scientific inquiry has pushed the envelope to ever smaller size scales, with sub-angstrom level resolution now available in many electron and atomic force microscopes. In this rush to increase resolution, however, a size scale has been largely skipped over. Long-range (>50Å) order has long been studied with diffraction techniques and is generally well known. Conversely, the short-range (<8Å) order is also relatively easily obtained via scattering techniques and the radial distribution function. Relatively little attention has been paid to length scales between these ranges, however. Recent studies have shown that understanding this medium-range order can often be the key to predicting properties and behavior in nominally amorphous materials.
Paul Voyles, University of Wisconsin, Madison, USA