Universitäre Service-Einrichtung für Transmissionselektronenmikroskopie
> Zum Inhalt

Electronic structure

DOS of TiC (from http://www.wien2k.at).

EELS-ELNES

The beam electrons excite different inelastic processes within the specimen. During the excitation they transfer energy to the sample. The determination of the ionisation energies and the respective intensities are used for chemical analysis. The shape of the ionisation edges is correlated with the density of unoccupied states (DOS) above the Fermi level. This attribute is used to deduce the bonding properties of the excited atoms by means of the ionisation edge fine structure (ELNES - Energy Loss Near Edge Structure). Simulation codes are accurate enough in order to apply a differential diagnosis of the electronic properties and chemical bondings of the solid state by comparing experiment and calculation.

 

At USTEM the Wien2k code based on the density functional theory is used for simulations. The following features can be calculated:

  •     Energy bands and density of states, energy loss spectra,
  •     Electron densities and spin densities, x-ray structure factors,
  •     Baders's "atoms-in-molecule" concept,
  •     Total energy, forces, equilibrium geometries, structure optimization, molecular dynamics,
  •     Phonons, with an interface to K.Parlinski's PHONON program
  •     Electric field gradients, isomer shifts, hyperfine fields,
  •     Spin-polarization (ferro- or anti-ferro- magnetic structures), spin-orbit coupling,
  •     X-ray emission and absorption spectra, electron energy loss spectra
  •     Optical properties,
  •     Fermi surfaces,
  •     LDA, GGA, meta-GGA, LDA+U, orbital polarization,
  •     Centro- or non-centro- symmetric cells, all 230 space groups built in