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First principles study of the isomer shift in Fe44M6Al50 (M = Ti, V, Cr, Co, Ni, Cu) alloys with B2 structure

Michalecki T., Deniszczyk J., Frąckowiak J.

Nukleonika

2004

Vol. 49,suppl.3

3-6

The 57Fe isomer shift for Fe44M6Al50 intermetallics with the B2 structure doped with M = Ti, V, Cr, Co, Ni and Cu additions has been calculated with the tight-binding linear muffin-tin orbital (TB-LMTO) method. The effect of variation of Wigner-Seitz (WS) spheres radii on the calculated equilibrium lattice parameter (a) and isomer shift (IS) was analyzed. The calculations have shown that the 57Fe isomer shift in Fe44M6Al50 intermetallics is directly proportional to the changes in the local 4s electronic charge at Fe atoms involved by M addtions. The screening effect of 4s electrons due to changes in (4p + 3d) electronic charge is of secondary importance. The calculated dependence of the average IS on nuclear charge (Z) of the alloying metal (M) follows qualitatively the tendency observed experimentally for the M impurities in the Fe host.

Ab initio study of the effect of pressure on the hyperfine parameters of 57Fe in bcc phase

Michalecki T., Deniszczyk J., Frąckowiak J.

Nukleonika

2003

Vol. 48,suppl.1

45-48

In this paper the results of studies on the effect of pressure on hyperfine magnetic field (Bf) and isomer shift (IS) for Fe-bcc are presented. Two calculation methods were used: TB-LMTO (Tight Binding Linear Muffin-Tin) and FP-LAPW (Full Potential Linearized Augmented Plane Wave) and the obtained results have been compared. Both methods lead to comparable results. In the study a particular emphasis has been laid on investigations of the atomic core electrons (1s, 2s, 3s) and of the conduction electrons 4s on the Bf and IS values. The calculated values of the dIS/dlnV and dlnB /dlnV parameters give evidence of good conformity with those derived from experimental data.