Knowledge of the atomic-scale structure is an important prerequisite to understand and control the properties of materials. In the case of crystals it is obtained solely from the Bragg peaks in their diffraction pattern and is given in terms of a small number of atoms placed in a unit cell subjected to symmetry constraints. However, many materials of technological importance, including nanophase materials, do not possess the long-range order and 3D periodicity of conventional crystals and it is this deviation from perfect order that makes them technologically and/or scientifically important. The diffraction patterns of such materials show a pronounced diffuse component and a few Bragg peaks, if any. This limits the applicability of the traditional techniques for structure determination and makes it difficult to obtain precise structural information needed in nanotechnology applications. In the talk we will show that this challenge can be met and the atomic-scale structure of nanocrystals determined by employing a nontraditional experimental approach going beyond the Bragg scattering in the diffraction data. The approach is that of the atomic pair distribution function technique (PDF). It takes both the diffuse and Bragg components of the diffraction data into account and yields the atomic ordering in terms of quantitative parameters such as a unit cell and symmetry even when the material is ordered only on the nanometer length scale. The talk will be illustrated with examples from successful structural studies on bulk nanocrystals such as LiMoS2(1), V2O5.nH2O nanoribbons(2, see Fig.1) and Cs nanoclusters (3, see Fig.2). New structural data for dendrimer nanoparticles and vanadium oxide nanotubes will be presented as well.
Journal: TechConnect Briefs
Volume: 3, Technical Proceedings of the 2004 NSTI Nanotechnology Conference and Trade Show, Volume 3
Published: March 7, 2004
Pages: 410 - 413
Industry sector: Sensors, MEMS, Electronics
Topics: Modeling & Simulation of Microsystems