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The inelastic scattering of X-ray
photons from electrons is known as
Compton scattering. The quantity
measured is Compton profile, J(pz), which is
the one-dimensional projection of the
momentum density ñ(p) on the scattering
vector. In transition metals the Fermi surface is very complex as the Fermi level intersects the d bands. Since wave functions of d bands are neither free electron like nor well localised in real space, the high momentum components play an important role in the formation of Compton profile. Therefore the transition metal compounds provide an important testing ground for Fermi surface geometry, wave function and momentum density. Comparision of band theoretical results yields information about the correlations of electrons in narrow bands. In this work we present the results of a Compton scattering study of two A15 compounds V3Ge and Cr3Ge. The measurements have been performed using 59.54 keV ã- rays from an 241Am source. The theoretical Compton profiles have been computed for both the compounds by using ab-initio linear combination of atomic orbitals (LCAO) method employing the CRYSTAL code of Torino group [3]. For both the compounds, the isotropic experimental and the theoretical profiles are found to be in good overall agreement. The comparison points out residual differences in the V3Ge whereas for Cr3Ge the differences are within experimental error. The behaviour of valence electrons in the two iso-structural compounds has been examined on the scale of Fermi momentum. The valence electrons distribution seems to be dominated by the metallic constituents rather than germanium and two compounds show covalent nature of bonding which is larger in V3Ge compared to Cr3Ge. |
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