Iterative LCAO treatment with overlap and band occupation in the iron-group metals

G. del Re , M. Kolár , F. Cyrot-Lackmann

A study of the LCAO scheme for the iron-group s- and d-bands is carried out with special emphasis on : (a) the choice of the AO basis and its adjustment to reproduce approaches like the renormalized-atom ansatz; (b) the dependence of the final results on overlap and the number of neighbours taken into account (s-band calculations require at least neighbours from up to the 12th shell, whereas for d-band 2nd neighbours are required at worst); (c) principle of Fermi-level equalization as a technique for determining the occupations and the relative positions of the s- and d-bands in an approximation neglecting s-d coupling. The results, obtained using quantum-chemical expressions for the « atomic » levels and for the hopping integrals, are consistent with the previous calculations, although they differ in many details. The estimated s-band occupation numbers for fcc Ni, Co and Fe are 0.85, 0.92 and 0.88, respectively, and the s-d separations (bottom of the s-band to the centre of the d-band) are 10.33 eV, 10.04 eV and 7.08 eV, respectively.

Mots clés: band structure of crystalline metals and alloys; band theory models and calculation methods; iterative methods; LCAO calculations; transition metals

Domaines: Articles anciens

G. del Re, M. Kolár, F. Cyrot-Lackmann. Iterative LCAO treatment with overlap and band occupation in the iron-group metals. Journal de Physique, 1985, 46 (6), pp.927-932. ⟨10.1051/jphys:01985004606092700⟩. ⟨jpa-00210038⟩