Electron Microscope Images of Icosahedral and Cuboctahedral (f.c.c. Packing) Clusters of Atoms

Abstract

Images have been computed of closed-shell clusters of 55, 147 or 309 atoms in regular icosahedral and cuboctahedral (f.c.c.) packing for an electron microscope operating at 100 keV, with Cs = 0·7 mm and resolutions of 0·3 and 0·2 nm. The object is to test the possibility of distinguishing the two structures from their images. The results show that sizes and shapes are well represented at optimum defocus but that similar images are often given by both structures. Discrimination could be made for some images at excessive underfocus at 0·2 nm resolution.