X-RAY DIFFRACTION OF INTERFACES IN NANOCRYSTALS. Yuming Wang and Kai Xing, Department of Materials Science, Jilin University, Changchun 130023, PR China

Fe and its oxides have been made in the form of nanocrystalline powders. The chemical as well as the vacuum deposition technologies were used to produce a great variety of microstructure, such as with different grain size, internal strain and inhomogeneity. The whole X-ray diffraction patterns of these samples were processed by Rietveld analysis using DBWS-9411 code supplied by Prof. R.A. Young. On the other side, the interfaces of these nanocrystals were simulated by molecular dynamics with several theoretical structural models. After sufficient atomic relaxation the interface structure reached equilibrium. Then the theoretical effect of interfaces on the whole X-ray diffraction pattern can be evaluated in detail. The comparison between the theoretical and experimental diffraction patterns gave a possibility to select the correct structural models as well as the interatomic potentials and related parameters. Using the correct interface structure one can predict a series of physical and mechanical properties of nanocrystals on a much sounder basis as compared to usual methods. This is important especially for those properties which are very difficult to measure experimentally.