High resolution studies of small particles of gold and silver. I. Multiply-twinned particles

The structure of multiply-twinned particles of gold and silver found in the early stages of particulate growth has been studied using direct lattice imaging methods with the Cambridge University 600 kV high resolution electron microscope. There was widespread evidence for the presence of strain-relieving partial dislocations in icosahedral particles. However, the possibility of imaging artefacts arising from double diffraction due to overlapping tetrahedral projections needed to be excluded, for example by slight particle tilting, before the actual presence of the dislocations was substantiated. An analysis of particle geometry, also including the effects of inhomogeneous strain, showed that straight Moiréfringes did not necessarily indicate the absence of strain within a particle. Moreover, it has been shown that, in some particle orientations, two different, though very similar, Moiré fringes can arise with their interaction and final appearance being very dependent on particle orientation.