Early stages in the addition to C60 to form C60Xn, X = H, F, Cl, Br, CH3, C4H9

The study of the early stages of addition to C-60 forming C60Xn has been extended to X = H, F, Cl, Br, CH3, C4H9, using the AMI Hamiltonian with the program MOPAC 6.0 and the density functional technique B3LYP/6-31G* with GAUSSIAN 98. For X = H, F, the density functional results show greater stability of structures based on addition to hex-hex edges than do the AM1 results. For X = Cl, Br, CH3, addition can either be on hex-hex edges or across the para positions of C-6 rings for C60X2. A combination of hex-hex addition and para addition can occur for C60X4, C60X6 and C60X12. Isomers with only para addition are found for C60X4, C60X8, C60X18 and C60X24. For C60Bu2, there is greater separation of the tert-butyl groups. (C) 2003 Elsevier Science B.V. All rights reserved.