Glass transition in single-crystal C60 studied by high-resolution dilatometry.

The thermal expansion of single-crystalline ${\mathrm{C}}_{6}$ is studied using high-resolution capacitance dilatometry. In addition to the orientational-ordering transition at 261 K, we observe a transition at ${\mathit{T}}_{\mathit{g}}$\ensuremath{\approxeq}90 K due to the freezing in of orientational disorder, which has the character of a glass transition. The relaxation near ${\mathit{T}}_{\mathit{g}}$ is studied by varying the heating (cooling) rate over more than two decades. It is found to obey an Arrhenius behavior with ${\mathit{E}}_{\mathit{a}}$=288\ifmmode\pm\else\textpm\fi{}5 meV within a simple glass-transition model.