Singular behaviour of small crystallites near the melting point

Abstract

DURING an extension of some recent in situ electron microscope investigations into the melting of small particles^1,2, some unexpected effects at temperatures near the melting point were observed for micron-sized crystallites of lead and bismuth. In particular, an unusually enhanced form of diffusion (termed ‘snapping’) occurred in which many crystallites changed their shapes abruptly into more compact solid forms. Experiments on somewhat smaller crystallites of tin have shown a similar behaviour. Changes of shape during the continuous deposition of thin films in an electron microscope have been reported by other workers^3,4; these, however, were of a more gradual character, and were consistent with normal diffusion processes.