INFRARED-ACTIVE MODES OF C-70

The infrared absorption intensity of a C70 molecule is calculated by a semi-empirical molecular orbital calculation library, mopac93. Geomet rical optimization for C70 is obtained by the MNDO and PM3 methods. Th e calculated molecular vibration frequencies of C70 at the optimized g eometry are shifted to higher frequency by about 15.5% compared with t he experimental result. The calculated result of the infrared absorpti on intensity shows that there are only 17 modes which have a large int ensity among the 31 infrared-active modes predicted by group theory. A comparison of the intensities of the infrared absorption spectra betw een theory and experiment is satisfactory.