Broken inter-C ₆₀ bonds as the cause of magnetism in polymeric C ₆₀: A density functional study using C ₆₀ dimers

Bond breaking in C 60-C 60 dimeric units is believed to play an important role in the onset of magnetism in 2D polymeric C 60. On the basis of density-functional theory, the calculations we present here provide further insight into this mechanism through a quantitative characterization of the bond-breaking processes in the isolated dumbbell-shaped C 60 dimer. In particular, the analysis of the calculated potential energy surfaces for the low-lying singlet and triplet states identifies and locates the S 0-T 2 crossing point, which is crucial for the transition to a magnetic state to take place under thermal conditions. These results also suggest a possible new approach to the production of magnetic polymeric C 60. © 2005 American Chemical Society.