  In this work, we perform first-principles calculations of the structural,
electronic, vibrational and magnetic properties of a novel ${\rm C}_{48}{\rm
N}_{12}$ azafullerene. Full geometrical optimization shows that ${\rm
C}_{48}{\rm N}_{12}$ is characterized by several distinguishing features: only
one nitrogen atom per pentagon, two nitrogen atoms preferentially sitting in
one hexagon, ${\rm S}_{6}$ symmetry, 6 unique nitrogen-carbon and 9 unique
carbon-carbon bond lengths. The highest occupied molecular orbital of ${\rm
C}_{48}{\rm N}_{12}$ is a doubly degenerate level of $a_{g}$ symmetry and its
lowest unoccupied molecular orbital is a nondegenerate level of $a_{u}$
symmetry. Vibrational frequency analysis predicts that ${\rm C}_{48}{\rm
N}_{12}$ has in total 116 vibrational modes: 58 infrared-active and 58
Raman-active modes. ${\rm C}_{48}{\rm N}_{12}$ is also characterized by 8
$^{13}{\rm C}$ and 2 $^{15}{\rm N}$ NMR spectral signals. Compared to ${\rm
C}_{60}$, ${\rm C}_{48}{\rm N}_{12}$ shows an enhanced third-order optical
nonlinearities which implies potential applications in optical limiting and
photonics.
