The role of substrate accommodation in the (111)- to (100)-state transition of gold particles on alkali halides

Annealing experiments on Au particles formed by vapour diffusion into shielded regions above air-cleaved NaCl and KCl substrates and subsequent nucleation has revealed significant differences in the ability of the substrates to cause reorientation of small crystallites by migration (causing (111)-azimuthal alignment) or internal atomic relaxation to the (100) epitaxial configuration. The observed phenomena support a recent theory governing epitaxial behaviour in the vacuum-deposited f.c.c. metal-alkali halide system. Strong evidence is obtained that secondary twinning on a {111}-based Au crystallite with 〈110〉_Au//〈100〉_subst is an intermediate stage in the atomic relaxation process encountered in the (111)- to (100)-state transition.