Date of Award

1983

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Abstract

A survey of previous theoretical and experimental works on iron in some Bravais lattices and at various temperature and pressures shows this 3d transition metal to exhibit a wealth of allotropic transformations and to possess, along with some of its alloys, peculiar magnetic properties in the face centered cubic (FCC) phase. We present an ab-initio self-consistent spin polarized band structure study of this metal in the body (BCC) and face centered cubic lattices at absolute zero and at various atomic volumes. Our calculations employed gaussian basis functions in a LCAO scheme and used the RSK local density potential. In contrast to previous attempts, the structural and atomic volume dependences of the electronic and magnetic states of iron are analysed using the fundamental parameters, band widths and exchange splittings, of the energy bands. While the smooth variation of the magnetic moment in BCC iron with lattice spacings greater or equal to 4.8 a.u. is attributed to the atomic origin of magnetism in that structural phase, its drastic change in FCC iron between a = 6.5516 a.u. and 7.0 a.u. is ascribed to a transition from an itinerant picture to a localized one. This analysis sheds some light on the nature of magnetism in other metals like cobalt. The relevance of the above transition to the properties of FCC iron based alloys is illustrated. Applications of the numerically established local quadratic dependence of the charge and spin form factors on the lattice spacing are discussed.

Pages

164

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