Article

Electronic structure of a σ-FeCr compound.

Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow, Poland.
Journal of Physics Condensed Matter (Impact Factor: 2.22). 06/2008; 20(23):235234. DOI: 10.1088/0953-8984/20/23/235234
Source: PubMed

ABSTRACT The electronic structure of a σ-FeCr compound in a paramagnetic state was calculated for the first time in terms of isomer shifts and quadrupole splittings. The former were calculated using the charge self-consistent Korringa-Kohn-Rostoker (KKR) Green's function technique, while the latter were estimated from an extended point charge model. The calculated quantities combined with recently measured site occupancies were successfully used to analyze a Mössbauer spectrum recorded at room temperature using only five fitting parameters namely background, total intensity, linewidth, IS0 (necessary to adjust the refined spectrum to the used Mössbauer source) and the QS proportionality factor. Theoretically determined changes of the isomer shift for the σ-FeCr sample were found to be in line with the corresponding ones measured on a α-FeCr sample.

Download full-text

Full-text

Available from: Janusz Tobola, Sep 23, 2014
0 Followers
 · 
136 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A series of sigma-phase Fe_{100-x}V_x samples with 34.4 < x < 59.0 were investigated by neutron and X-ray diffraction and Mossbauer spectroscopy (MS) techniques. The first two methods were used for verification of the transformation from alpha to sigma phase and they also permitted to determine lattice parameters of the unit cell. With MS the Debye temperature, T_D, was evaluated from the temperature dependence of the centre shift, , assuming its entire temperature dependence originates from the second-order Doppler shift. To our best knowledge, it is the first ever-reported study on T_D in sigma-FeV alloys. Both attice parameters i.e. a and c were revealed to linearly increase with x. T_D shows, however, a non-monotonic behaviour as a function of composition with its extreme values between 425K for x=40 and 600K for x=59. A local maximum of 525K was found to exist at x=43.
    Intermetallics 03/2010; 18(8). DOI:10.1016/j.intermet.2010.05.010 · 2.12 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Neutron powder diffraction was used to study the distribution of Co and Cr atoms over different lattice sites as well as the lattice parameters of sigma-phase compounds Co(100 - x)Cr(x) with x = 57.0, 62.7 and 65.8. From the diffractograms recorded in the temperature range of 4.2-300 K it was found for the five crystallographically independent sites that A (2a) and D (8i) are predominantly occupied by Co atoms, while sites B (4f), C (8i) and E (8j) mainly accommodate Cr atoms. The lattice parameters a and c exhibit linear temperature dependencies, with different expansion coefficients in the temperature ranges of 4.2-100 and 100-300 K.
    Acta crystallographica. Section B, Structural science 04/2012; 68(Pt 2):123-7. DOI:10.1107/S0108768112006234 · 2.10 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Structural (lattice parameters and sublattice occupancies) and electronic (charge-density and electric field gradient) properties in a series of compounds mu-Fe_(100-x)Mo_x were studied experimentally (X-ray diffraction and Mossbauer spectroscopy) and theoretically (charge and spin self-consistent KorringaKohnRostoker Green function method). The lattice parameters a and c showed a linear increase with x while all five lattice sites were found to be populated by both alloying elements: A and B predominantly by Fe atoms whereas C and D by Mo atoms hardly depending on the composition. The population of Fe atoms on the site E was ranging between ca. 50% at x=37.5 and ca. 20% at x=44.5. Fe-site charge-density (isomer shift) and the electric field gradient (quadrupole splitting, QS) were revealed to be characteristic of the lattice site and both of them were almost x-independent. The difference in the charge-density at Fe-atoms at the sites B (the highest value) and those at the sites D (the lowest value) was estimated as equivalent to 0.18 electrons. The average charge-density increases linearly with x. The largest QS-values were those at the sites A and C, while the smallest ones at the site D.
    Journal of Alloys and Compounds 12/2013; 612. DOI:10.1016/j.jallcom.2014.05.201 · 2.73 Impact Factor