Quantitative X-ray diffraction study of the atomic structure of the ∑ = 5( θ = 36.9°) [001]twist boundary in gold

Abstract

Quantitative X-ray diffraction techniques have been used to determine the structure of the large angle ∑ = 5( θ = 36.9°)[001]twist boundary in Au to a resolution of better than ±0.09Å. Large portions of the reciprocal lattice in three dimensions were mapped out using synchrotron radiation. The atomic structure was obtained by testing model structures against the intensity observations with a χ 2 analysis. Details of the atomic structure of the grain boundary, including measurement of the magnitude of the expansion at the interface, are presented. The grain boundary structure was shown to consist of arrays of two kinds of distorted octahedra and special configurations of distorted tetrahedra interwoven together by the boundary symmetry. This work points to the possibility of obtaining Pauling's type rules for grain boundary structures based on X-ray diffraction observations that give the atomic positions with high resolution. Studies were performed to search for diffraction effects that are expected to be caused by structural multiplicity of the boundary, and no evidence for its occurrence was found.