Relative stabilities are calculated with the density-functional based tight
-binding method for all isomers C36H2x (x = 1, 2, 3) based on the two C-36
classical fullerenes with minimal pentagon adjacencies. Preferential additi
on at pentagon junctions leads to low-energy candidates for C36H4 and C36H6
based on the sixfold-symmetric cylindrical C-36 fullerene cage, 36 : 15.