Double tetrahedra in quenched gold

Abstract

Double tetrahedra consisting of two equally sized stacking-fault tetrahedra sharing an edge have been systematically observed by electron microscopy in gold quenched from 900°C. However, they are not formed when the quenching temperature is raised to near the melting point. The geometry of these defects has been confirmed by stereomicroscopy. By calculating the energy of the defect to a first approximation, it can be shown that a double tetrahedron in which the two units are of equal size is metastable with respect to a single tetrahedron containing the same number of vacancies. No triple or higher-order tetrahedron has been found.