Electronic Structures of Transition-Metal Pernitrides Studied Using X-ray Absorption and Photoelectron Spectroscopy

The electronic structure of newly synthesized marcasite-type cobalt pernitride (CoN2) is investigated using X-ray absorption and photoelectron spectroscopy (XAS and XPS), in combination with the electronic band structure calculation within the scheme of the density functional theory under a generalized gradient approximation. N K-edge XAS spectra and unoccupied electronic structures of the marcasite-type RuN2 and pyrite-type PtN2 are also studied. The N K-edge XAS and valence-band XPS spectra are well explained using the calculated valence-band and conductionband densities of states, which agree well with the XAS spectra calculated using the electric dipole approximation. The physical properties of these pernitrides are discussed in terms of the obtained electronic structures. In contrast to the Pt-4(+) 5d-t(2g)(6) configuration, which leads to the strong covalent nature and insulating superhard properties of the pyritetype PtN2, the ferromagnetic metal of the marcasite-type CoN2 can he derived from the Co2+ 3d-t(2g)(6)e(g)(1) configuration instead of the Co4+ 3d-t(2g)(5)( )configuration. The difference in the electronic configurations of the Co pernitride is attributed to the spatial extent of the 3d states.

Automated summary

The electronic structure of newly synthesized marcasite-type cobalt pernitride (CoN2) was investigated using XAS and XPS, and the physical properties were discussed in terms of the obtained electronic structures. In contrast to pyrite-type pernitrides, marcasite-type cobalt pernitride exhibits ferromagnetic metal properties.