Valence Band Form of the Ferroelectric SbSI Crystal

The electronic structure of the valence band (VB) of the ferroelectric SbSI crystal was calculated by solving the Hartree-Fock-Roothan matrix equation FC=SCε. The diagonal matrix ε gives the electron state energies [8,9]. These energies experimentally were also studied by PHI 5700/660 Physical Electronics Spectrometer using as excitation source Al Ka monochromatic radiation (1486.6 eV). The spectrum of the VB electronic levels was approximated by the Gauss functions. The form of the VB depends of the width of the Gauss function and the number of SbSI molecules, which were taken into account in the model of the SbSI crystal. The obtained theoretical density of states and VB form of SbSI crystal is close to the experimental