ELECTRONIC STRUCTURE AND CHEMICAL BONDING IN ALKALINE EARTH METAL SUBNITRIDES: PHOTOEMISSION STUDIES AND BAND STRUCTURE CALCULATIONS

Abstract

Listen

Translate article

The electronic structure of various alkaline earth metal subnitrides has been studied by X-ray and ultraviolet photoelectron spectroscopy and by LMTO band structure calculations. Improved methods for the synthesis of several of the materials are described. The electronic structure of compounds with discrete clusters (Na 22Ba 14SrN 6) or Ba 3N chains (Ba 3N, NaBa 3N, Na 5Ba 3N) in the crystal structure is characterized by a narrow atomic-like N-2p band occurring between 2 and 2.5 eV in the photoemission spectra. The spectra and the results from the band structure calculations support the idea of ionic bonding between N 3− ions and surrounding partly oxidized alkaline earth metal atoms. The N-2p regions in valence band spectra and density-of-states curves of Ca 2N, Sr 2N and Ba 2N, which have layered crystal structures, extend over a broader energy range, suggesting a more pronounced dispersion of the N-2p band in these compounds. Several feature seen in NeI, HeI, NeII and HeII spectra of the series M 2N are assigned to Auger transitions involving a primary hole in a shallow core level (N-2s or M- np) and either electrons from the metal valence band or from N-2p levels.