Searching for stable fullerenes in space with computational chemistry
  We report a computational study of the stability and infrared (IR)
vibrational spectra of neutral and singly ionised fullerene cages containing
between 44 and 70 carbon atoms. The stability is characterised in terms of the
standard enthalpy of formation per CC bond, the HOMO-LUMO gap, and the energy
required to eliminate a C$_2$ fragment. We compare the simulated IR spectra of
these fullerene species to the observed emission spectra of several planetary
nebulae (Tc 1, SMP SMC 16, and SMP LMC 56) where strong C$_{60}$ emission has
been detected. Although we could not conclusively identify fullerenes other
than C$_{60}$ and C$_{70}$, our results point to the possible presence of
smaller (44, 50, and 56-atom) cages in those astronomical objects.
Observational confirmation of our prediction should become possible when the
James Webb Space Telescope comes online.
