Theoretical investigations on the spectroscopic and third order nonlinear optical properties of C₁₀₆ isolated pentagon rule fullerenes

The lowest lying 10 isomers of C₁₀₆ satisfying the isolated pentagon rule (IPR) were predicted from 1233 IPR isomers with semiempirical and density functional theory based methods. The structures, stabilities, IR and UV spectroscopic, and the third order nonlinear optical (NLO) properties of those low lying isomers were explored in detail. C_s:331, C₂:1194, and C₁:534 are the three lowest energy isomers with almost identical energies and could be observed in experiment. When the entropy effects in the isomeric fullerene system are taken into account, isomer C₂:1194 prevails up to 3000 °C. In the high temperature region, the concentrations of those ten low lying isomers are very similar, indicating that the isomers at high temperatures will be hard to isolate. The third order NLO properties under external fields (0.0 3.0 eV) of the five lowest lying isomers were analyzed, and the average NLO properties of those isomers were predicted at room temperature for experimental exploration.