Comment to "Imaging the atomic orbitals of carbon atomic chains with field-emission electron microscopy"

The observation of a stable doublet pattern in the field-emission electron microscopy of a linear atomic chain requires a stable mechanism breaking the axial symmetry, which is not identified correctly by Mikhailovskij et al. [Phys. Rev. B 80, 165404 (2009)]. Using microscopic calculations, we attribute the observed pattern to the symmetry breaking produced by the ligand where the chain is attached, plus carbon pi-bonding alternation.Comment: 2 pages 1 fig, PRB commen

An optimized algebraic basis for molecular potentials

The computation of vibrational spectra of diatomic molecules through the exact diagonalization of algebraically determined matrixes based on powers of Morse coordinates is made substantially more efficient by choosing a properly adapted quantum-mechanical basis, specifically tuned to the molecular potential. A substantial improvement is achieved while still retaining the full advantage of the simplicity and numerical light-weightedness of an algebraic approach. In the scheme we propose, the basis is parameterized by two quantities which can be adjusted to best suit the molecular potential through a simple minimization procedure.Comment: 29 pages, 4 tables and 4 figures, latex. Sumbitted to J. Phys. Chem

Jahn-Teller distortions and excitation energies in C60(n+)

Based on previously computed parameters for the electron-phonon couplings and the Coulomb exchange, we compute and classify the static Jahn-Teller distortions, i.e. the minima of the lowest adiabatic potential energy surface, of C60(n+), for all values of charge 1 <= n <= 9 and spin. We compute the intra-band electronic excitation energies in the different optimal geometries in the sudden approximation, and find a spread of the electronic states of roughly 1 eV. We also obtain the leading vibronic quantum corrections to the ground-state energy, equal to zero-point energy lowering due to the softening of the phonons at the adiabatic Jahn-Teller minima: these non-adiabatic corrections are so large that for 4 <= n <= 6 states of different spin symmetry turn lower than the high-spin adiabatic ground state.Comment: 19 pages, proceedings of the XVI Jahn-Teller Conference - Leuven (Be), 26/8 - 1/9 200

Thermal formation of carbynes

We simulate the formation of $sp$ carbon chains (carbynes) by thermal decomposition of $sp^2$ carbon heated by a hot discharge plasma, by means of tight-binding molecular dynamics. We obtain and analyze the total quantity of carbynes and their length distribution as a function of temperature and density

Jahn-Teller Spectral Fingerprint in Molecular Photoemission: C60

The h_u hole spectral intensity for C60 -> C60+ molecular photoemission is calculated at finite temperature by a parameter-free Lanczos diagonalization of the electron-vibration Hamiltonian, including the full 8 H_g, 6 G_g, and 2 A_g mode couplings. The computed spectrum at 800 K is in striking agreement with gas-phase data. The energy separation of the first main shoulder from the main photoemission peak, 230 meV in C60, is shown to measure directly and rather generally the strength of the final-state Jahn-Teller coupling.Comment: 5 pages, 3 figure