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

TL;DR

This study observes a phase transition in the equilibrium shape of oxygen-covered tungsten crystals, where the vertex becomes rounded at approximately 970 K, indicating a vertex-rounding transition.

Contribution

First direct observation of the vertex-rounding transition in oxygen-covered tungsten using field ion microscopy.

Findings

Vertex-rounding transition occurs near 970 K.

Crystal shape changes from polyhedral to rounded at the vertex.

Transition temperature has an uncertainty of ±70 K.

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 $970\pm70$ K, the system undergoes a phase transition from a polyhedral form (sharp edges and sharp vertex) to a rounded form (sharp edges, rounded vertex).