ELECTRONIC-STRUCTURE OF THE LEAD MONOXIDES - BAND-STRUCTURE CALCULATIONS AND PHOTOELECTRON-SPECTRA

PbO is a layer compound which exists in two polymorphic forms, a red t etragonal (alpha) and a yellow orthorhombic (beta) modification. Ab in itio band-structure calculations are presented for both phases. The ca lculated energy gaps are in agreement with optical data. The band-stru cture calculations are used to discuss the chemical bonding in the alp ha and beta phases. It is found that the Pb 6s states are strongly hyb ridized with O 2p orbitals. Thus the so-called Pb (6s)(2) lone pair in PbO takes part in the chemical bonding, and cannot be considered as a n inert pair. Photoelectron spectra of the valence band and of some co re levels are presented for alpha- and beta-PbO. The observed valence band is in good agreement with the calculated band structure.