Ab initio calculation results for the electronic structure of disordered bcc Fe x Al 1Ϫx (0.4Ͻx Ͻ0.75), Co x Al 1Ϫx , and Ni x Al 1Ϫx (xϭ0.4;0.5;0.6) alloys near the 1:1 stoichiometry, as well as of the ordered B2 ͑FeAl, CoAl, NiAl͒ phases with point defects are presented. The calculations were performed using the coherent potential approximation within the Korringa-Kohn-Rostoker method for the disordered case and the tight-binding linear muffin-tin orbital method for the intermetallic compounds. We studied in particular the onset of magnetism in Fe-Al and Co-Al systems as a function of the defect structure. We found the appearance of large local magnetic moments associated with the transition metal ͑TM͒ antisite defect in FeAl and CoAl compounds, in agreement with the experimental findings. Moreover, we found that any vacancies on both sublattices enhance the magnetic moments via reducing the charge transfer to a TM atom. Disordered Fe-Al alloys are ferromagnetically ordered for the whole range of composition studied, whereas Co-Al becomes magnetic only for Co concentration у0.5. ͓S0163-1829͑99͒00910-8͔

No abstract

No abstract

No abstract

The rotational structure of six bands of the TbO molecule, including the 0–0 bands of electronic transitions III, IV, and V, was analyzed using laser excitation spectroscopy with selective fluorescence detection. From the fluorescence spectra obtained through excitation of selected rotational lines in these bands, the energies of 14 low-lying Ω states as well as ΔG1/2 values for the four lowest Ω states were determined. The values of Ω and rotational constants B and D were found for each, low-lying state and the upper states of the analyzed bands; an energy linkage for all the electronic transitions, whose rotational structure has been analyzed, is established. The ground state constants of TbO are (2σ—uncertainty in parentheses) Ω = 6.5, B0 = 0.3525(1) cm−1, D0 = 1.8(2) × 10−7 cm−1, ΔG1/2 = 837.1(1) cm−1, α = 1.5(1) × 10−3 cm−1.