The configuration of atomic defects as determined from scattering studies

Abstract

Atomic defects such as vacancies and interstitials in crystalline solids produce elastic diffuse scattering of X-rays or neutrons. The distribution in reciprocal space of the diffuse scattering intensity contains very direct information about the atomic structure of point defects, and it sensitively shows the formation of defect clusters. Three domains of the scattering are distinguished: (a) scattering in the forward direction (small-angle scattering); (b) scattering between the Bragg reflections; and (c) scattering close to the Bragg reflections (Huang scattering). The specific features of the information obtained from measurements in the different domains are discussed. Experimental results on the structure of interstitials in metals have been obtained after low temperature electron irradiation of the fcc metals Al and Cu, bcc Mo, and hcp Zn. In other metals (Au, Nb, Cd, Mg) the agglomeration of interstitials was observed during electron irradiation at 5 K.