Physics Of Grain Boundaries Research Articles

Universal trends in computed grain boundary energies of FCC metals

We use a simple parameterization of the Embedded Atom Method (EAM), termed EAM-X, to explore the dependence of grain boundary (GB) energies in FCC metals on EAM parameters. We study a set of GBs with various geometries and calculate their energies, scanning through EAM-X parameter space. We find that variations in GB energy with EAM parameters can be larger than variations due to GB geometry. The atomistic data are used to determine a fit of the GB energy in EAM parameter space, which can be used to obtain boundary energies in real FCC elements without the need to perform new atomistic calculations. Our results provide broad confirmation of a proposed correlation between calculated GB energy and shear modulii among FCC metals. Our work also highlights the need to consider sensitivity to details of empirical potentials when performing quantitative studies of GB physics.

EBSD Characterization of Specific Microstructures in RE-BCO Superconductors

Using the electron backscatter diffraction (EBSD) technique, we analyze in this contribution the microstructure of YBa2Cu3O x (YBCO) thick films with embedded a -axis oriented grains. The YBCO films were prepared by liquid phase epitaxy in air using NdGaO3 substrates. Using this technique, a / c -grain boundaries (GBs) with a well-defined facet of the YBCO film characterized by a single crystalline nature are obtained. This type of GB is very important for the basic physics of GBs in high- T c superconductor materials, and will contribute to a better understanding of GBs also in bulk materials. The application of EBSD to the analysis of a / c -GBs in YBCO requires a high Kikuchi pattern quality (i.e., image quality) to enable a proper distinction of the orientation, as the a -axis corresponds to about one-third of the c -axis, which can cause a misinterpretation of the resulting data. Having solved this problem, the EBSD-based determination of the GB misorientation angles directly proof the specific grain orientation achieved in the film growth.