Observation of vertex-rounding transition for a crystal in equilibrium: Oxygen-covered tungsten

Abstract

Equilibrium crystal shape of oxygen-covered tungsten is followed as a function of temperature using field ion microscopy. In the vicinity of the (111) region, at the temperature $970\ifmmode\pm\else\textpm\fi{}70\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, the system undergoes a phase transition from a polyhedral form (sharp edges and sharp vertex) to a rounded form (sharp edges, rounded vertex).