POTASSIUM-DOPED FULLERENE KXC60 WITH X = 0,1,2,3,4, AND 6

The potassium doping of C60 to KxC60 with 0 less-than-or-equal-to x less-than-or-equal-to 6 was studied by Raman spectroscopy at temperatures slightly above room temperature. A new phase with x = 1 was found. This phase decays at a temperature of 80-degrees-C into C60 and K3C60. For potassium concentrations above x = 3 a stoichiometric phase with x = 4 and diluted structures with x less-than-or-equal-to 6 were observed. The x = 6, 3, and 1 structures revealed a strictly linear relation between charge on the C60 and position of the Raman line for the pinch mode. This suggests that the pinch mode has the frequency 1464.5 cm-1 at 90-degrees-C and 1466 cm-1 at room temperature.