Secondary Twinning in Electron-Diffraction Patterns of Nickel Films Epitaxially Grown

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Abstract
Nickel films epitaxially grown were obtained by high‐vacuum evaporation on rocksalt faces cleaved in air. They were partially oriented and their thickness was 800 Å. The electron‐diffraction pattern was interpreted assuming the presence of primary and secondary twins and the orientation (001) parallel to the substrate. The composite reciprocal lattice, containing points from the matrix and from primary and secondary twins, was calculated by means of a computer program. The symmetry elements of this lattice permit the deduction of a selection rule to determine the location of the secondary twinned points with respect to those of the matrix and a cubic supercell with nine unitary cells along each orthogonal axis. The double diffraction points, arising from beams rediffracted in secondary twins, explain the origin of the rings interior to the (111).