Electronic structure and stability of thorium carbonitrides

The electronic structure of the monoclinic (α-ThCN), hexagonal (β-ThCN) and cubic (ThCxN1-x) thorium carbonitrides is studied within the density-functional theory (DFT). We predict the metal conductivity for the solid solutions ThCxN1-x, but both α-ThCN and β-ThCN phases should be semiconductors with band gap 1.49 eV and 1.97 eV, respectively. Distinct from the 5f metal carbides and nitrides, both Th 6d and Th 5f states give comparable contributions to the density of states at the Fermi level in ThCxN1-x. The enthalpies of formation were estimated relative to the different reagents and the largest values were obtained for the reactions with simple reagents (α-Th,C,N). (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)