Rui-Hua Xie

First-principles calculations of structural, electronic, vibrational, and magnetic properties of C-60 and C48N12: A comparative study

The structural, electronic, vibrational, and magnetic properties of the C48N12 azafullerene and C60 are comparatively studied from the first-principles calculations. Full geometrical optimization and Mulliken charge analysis are performed. Electronic structure calculations of C48N12 show that the highest occupied molecular orbital (HOMO) is a doubly degenerate level of ag symmetry and the lowest unoccupied molecular orbital (LUMO) is a nondegenerate level of au symmetry. The calculated binding energy per atom and HOMO-LUMO energy gap of C48N12 are about 1 eV smaller than those of C60. 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 C48N12 is about 55% larger than that of C60. Our vibrational frequency analysis predicts that C48N12 has 58 infrared-active and 58 Raman-active vibrational modes. Two different methods for calculating nuclear magnetic shielding tensors of C60 and C48N12...

Electronic, vibrational and magnetic properties of a novel C48N12 aza-fullerene

Abstract The structural, electronic, vibrational and magnetic properties of a novel C 48 N 12 aza-fullerene are studied by using density functional and Hartree–Fock methods. Optimized geometries and total energy of this aza-fullerene are calculated. The HOMO–LUMO gap of C 48 N 12 is found to be about 1 eV smaller than that of C 60 . Fifty-eight IR-active frequencies and 10 NMR spectral signals are predicted for C 48 N 12 . Diamagnetic shielding factor, polarizability and hyperpolarizability of C 48 N 12 are calculated. Our results suggest that C 48 N 12 may have potential applications as semiconductor components and possible building materials for nanometer electronics, photonic devices and diamagnetic superconductors.

Excitations, Optical Absorption Spectra, and Optical Excitonic Gaps of Heterofullerenes: I. C60, C59N+ and C48N12: Theory and Experiment

Low-energy excitations and optical absorption spectrum of C(60) are computed by using time-dependent (TD) Hartree-Fock, TD-density functional theory (TD-DFT), TD DFT-based tight-binding (TD-DFT-TB), and a semiempirical Zerner intermediate neglect of diatomic differential overlap method. A detailed comparison of experiment and theory for the excitation energies, optical gap, and absorption spectrum of C(60) is presented. It is found that electron correlations and correlation of excitations play important roles in accurately assigning the spectral features of C(60), and that the TD-DFT method with nonhybrid functionals or a local spin density approximation leads to more accurate excitation energies than with hybrid functionals. The level of agreement between theory and experiment for C(60) justifies similar calculations of the excitations and optical absorption spectrum of a monomeric azafullerene cation C(59)N(+), to serve as a spectroscopy reference for the characterization of carborane anion salts. Although it is an isoelectronic analogue to C(60), C(59)N(+) exhibits distinguishing spectral features different from C(60): (1) the first singlet is dipole-allowed and the optical gap is redshifted by 1.44 eV; (2) several weaker absorption maxima occur in the visible region; (3) the transient triplet-triplet absorption at 1.60 eV (775 nm) is much broader and the decay of the triplet state is much faster. The calculated spectra of C(59)N(+) characterize and explain well the measured ultraviolet-visible (UV-vis) and transient absorption spectra of the carborane anion salt [C(59)N][Ag(CB(11)H(6)Cl(6))(2)] [Kim et al., J. Am. Chem. Soc. 125, 4024 (2003)]. For the most stable isomer of C(48)N(12), we predict that the first singlet is dipole-allowed, the optical gap is redshifted by 1.22 eV relative to that of C(60), and optical absorption maxima occur at 585, 528, 443, 363, 340, 314, and 303 nm. We point out that the characterization of the UV-vis and transient absorption spectra of C(48)N(12) isomers is helpful in distinguishing the isomer structures required for applications in molecular electronics. For C(59)N(+) and C(48)N(12) as well as C(60), TD-DFT-TB yields reasonable agreement with TD-DFT calculations at a highly reduced cost. Our study suggests that C(60), C(59)N(+), and C(48)N(12), which differ in their optical gaps, have potential applications in polymer science, biology, and medicine as single-molecule fluorescent probes, in photovoltaics as the n-type emitter and/or p-type base of a p-n junction solar cell, and in nanoelectronics as fluorescence-based sensors and switches.

Structural, electronic, and magnetic properties of heterofullerene C48B12

Bonding, electric (hyper)polarizability, vibrational, and magnetic properties of heterofullerene C48B12 are studied by first-principles calculations. Infrared- and Raman-active vibrational frequencies Of C48B12 are assigned. Eight C-13 and two B-11 nuclear magnetic resonance (NMR) spectral signals Of C48B12 are characterized. The average second hyper-polarizability of C48B12 is about 180% larger than that of C-60. Our results suggest that C48B12 is a candidate for photonic and optical limiting applications because of the enhanced third-order optical non-linearities

Raman scattering in C60 and C48N12 aza-fullerene: First-principles study

We carry out large-scale ab initio calculations of Raman scattering activities and Raman-active frequencies (RAFs) in

Optical excitation and absorption spectra of C50Cl10.

{\mathrm{C}}_{48}{\mathrm{N}}_{12}

Structure, Stability, and NMR Properties of Lower Fullerenes C38−C50 and Azafullerene C44N6

aza-fullerene. The results are compared with those of

Cluster-assembled materials based onNa6Pb

{\mathrm{C}}_{60}.

Electron-hole correlations and optical excitonic gaps in quantum-dot quantum wells: Tight-binding approach

Twenty-nine nondegenerate polarized and 29 doubly degenerate unpolarized RAFs are predicted for

Density functional study of onion-skin-like [As@Ni12As20]3− and [Sb@Pd12Sb20]3− cluster ions

{\mathrm{C}}_{48}{\mathrm{N}}_{12}.