FULLERENE C-78 ISOMERS - TEMPERATURE-DEPENDENCE OF THEIR CALCULATED RELATIVE STABILITIES

Abstract

C78 is treated as a system composed of five local minima (D3h(I), D3h(II), D3, C2v(I), and C2v(II)) whose energies, geometries and vibrational frequencies are obtained from MNDO calculations. The AMI and PM3 energy data are also considered. The predicted global minimum (C2v(II)) remains the most stable species of the equilibrium isomeric mixture even at high temperatures, and the D3h(I) structure is negligible throughout. The remaining three species exhibit comparable stabilities and make up nearly 50% of the high temperature mixture. The recently observed ratio of 1:5 of the D3 and C2v(I) structures is reached at temperatures of 1308 K, 734 K and 980 K for the MNDO, AMI and PM3 energetics respectively.