Structure of Rb:C60compounds

Abstract

We report x-ray-diffraction studies on ${\mathrm{Rb}}_{\mathit{x}}$ ${\mathrm{C}}_{60}$ samples of nominal composition ranging from x=1.5 to 6. After six weeks of annealing at 200 °C, we observe well-defined stoichiometric compounds ${\mathrm{Rb}}_{\mathit{n}}$ ${\mathrm{C}}_{60}$ with n=0 (pure ${\mathrm{C}}_{60}$), 3, 4, and 6, and refine the corresponding face-centered cubic, body-centered tetragonal, and body-centered cubic structures. Evidence is found for a fifth compound as well. The n=3 and 6 structures are analogous to the corresponding ${\mathrm{K}}_{\mathit{n}}$ ${\mathrm{C}}_{60}$ compounds.