Mechanically induced chemical decomposition ofC60-n-pentane clathrate at room temperature

We report the mechanically induced chemical decomposition of ${\mathrm{C}}_{60}$-n-pentane. This material is a typical ${\mathrm{C}}_{60}$ clathrate with a well-characterized structure and is stable up to 400 K. However, at room temperature the grinding of ${\mathrm{C}}_{60\mathrm{-}}$n-pentane induces the loss of n-pentane from the originally orthorhombic structure and the material transforms to pure ${\mathrm{C}}_{60}$ with the face-centered-cubic structure. The average crystallite size of the final powder is quite small, from x-ray powder-diffraction peak widths it is estimated to be 150 Å. This unusual chemical decomposition at room temperature points to the highly strained nature of the structure. Similar chemical decomposition might exist for other ${\mathrm{C}}_{60}$ clathrates such as ${\mathrm{C}}_{60}$ acetone.