First-principles calculations of the structural, electronic, vibrational and magnetic properties of C_{60} and C_{48}N_{12}: a comparative study

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.Comment: a long version of our manuscript submitted to J.Chem.Phy

First-principles calculations of structural, electronic, vibrational, and magnetic properties of C60 and C48N12: A comparative study

The structural, electronic, vibrational, and magnetic properties of the C 48 N 12 azafullerene and C 60 are comparatively studied from the first-principles calculations. Full geometrical optimization and Mulliken charge analysis are performed. Electronic structure calculations of C 48 N 12 show that the highest occupied molecular orbital (HOMO) is a doubly degenerate level of a g symmetry and the lowest unoccupied molecular orbital (LUMO) is a nondegenerate level of a u symmetry. The calculated binding energy per atom and HOMO-LUMO energy gap of C 48 N 12 are about 1 eV smaller than those of C 60 . Because of electron correlations, the HOMO-LUMO gap decreases about 5 eV and the binding energy per atom increases about 2 eV. The average second-order hyperpolarizability of C 48 N 12 is about 55% larger than that of C 60 . Our vibrational frequency analysis predicts that C 48 N 12 has 58 infrared-active and 58 Raman-active vibrational modes. Two different methods for calculating nuclear magnetic shieldingtensors of C 60 and C 48 N 12 are compared, and we find that C 48 N 12 exhibits eight 13 C and two 15 N NMRspectral signals. Our best-calculated results for C 60 are in excellent agreement with experiment. Our results suggest that C 48 N 12 has potential applications as semiconductor components, nonlinear optical materials, and possible building blocks for molecular electronics and photonic devices

Electronic, vibrational and magnetic properties of a novel C_{48}N_{12} aza-fullerene

We study the structural, electronic, vibrational and magnetic properties of a novel ${\rm C}_{48}{\rm N}_{12}$ aza-fullerene using density functional theory and restricted Hartree-Fock theory. Optimized geometries and total energy of this fullerene have been calculated. We find that for ${\rm C}_{48}{\rm N}_{12}$ the total ground state energy is about -67617 eV, the HOMO-LUMO gap is about 1.9 eV, five strong IR spectral lines are located at the vibrational frequencies, 461.5 ${\rm cm}^{-1}$, 568.4 ${\rm cm}^{-1}$, 579.3 ${\rm cm}^{-1}$, 1236.1 ${\rm cm}^{-1}$, 1338.9 ${\rm cm}^{-1}$, the Raman scattering activities and depolarization ratios are zero, and 10 NMR spectral signals are predicted. Calculations of diamagnetic shielding factor, static dipole polarizabilities and hyperpolarizabilities of ${\rm C}_{48}{\rm N}_{12}$ are performed and discussed.Comment: published in Chem.Phys.Let

Tailorable Acceptor C 60 − n B n and Donor C 60 − m N m Pairs for Molecular Electronics

Our first-principles calculations demonstrate that C 60-n B n /C 60-m Nm molecules could be engineered acceptor/donor pair needed for molecular electronics by properly controlling the number n and m of the substitutional dopants in C 60 . As an example, we propose that acceptor C 48 B 12 and donor C48 N12 can be promising components for molecular rectifiers, nanotube-based p-type, n-type and n-p-n transistors and p-n junctions

Raman scattering in C_{60} and C_{48}N_{12} aza-fullerene: First-principles study

We carry out large scale {\sl ab initio} calculations of Raman scattering activities and Raman-active frequencies (RAFs) in ${\rm C}_{48}{\rm N}_{12}$ aza-fullerene. The results are compared with those of ${\rm C}_{60}$. Twenty-nine non-degenerate polarized and 29 doubly-degenerate unpolarized RAFs are predicted for ${\rm C}_{48}{\rm N}_{12}$. The RAF of the strongest Raman signal in the low- and high-frequency regions and the lowest and highest RAFs for ${\rm C}_{48}{\rm N}_{12}$ are almost the same as those of ${\rm C}_{60}$. The study of ${\rm C}_{60}$ reveals the importance of electron correlations and the choice of basis sets in the {\sl ab initio} calculations. Our best calculated results for ${\rm C}_{60}$ with the B3LYP hybrid density functional theory are in excellent agreement with experiment and demonstrate the desirable efficiency and accuracy of this theory for obtaining quantitative information on the vibrational properties of these molecules.Comment: submitted to Phys.Rev.