The complete set of seven isolated-pentagon-rule isomers of C-80 is de
scribed by the AM1 quantum-chemical method, and their energetics is al
so checked by the SAM1 computations. Considerable temperature effects
on the relative stabilities in the system are reported. The ground-sta
te structure is a D-5d isomer but at supposed synthetic conditions a s
tructure of a D-2 symmetry is the most populated one.