Abstract
MNDO calculations with complete geometry optimization are reported for 30 polyhedral carbon clusters Cn (20 ≤ n ≤ 540). The MNDO results for a planar graphite sheet are extrapolated from calculations on D6h hydrocarbons CnHm,
(n = 6k2, m = 6k, k = 1-6) and used as a reference for discussing the properties of the clusters. The structural features of the clusters are correlated with their stability. The relative MNDO energies with respect to graphite are compared with
curvature-corrected Hückel calculations and with force field estimates, and criteria for the stability of the clusters are discussed.
Infrared spectra are predicted for six stable clusters. Several cationic lithium complexes and their interconversions are investigated
for C60 and C42. Finally, computational aspects and performance data are considered, particularly for the largest clusters studied.
