Onset of magnetism in B2 transition metals aluminides

Ab initio calculation results for the electronic structure of disordered bcc Fe(x)Al(1-x) (0.4<x<0.75), Co(x)Al(1-x) and Ni(x)Al(1-x) (x=0.4; 0.5; 0.6) alloys near the 1:1 stoichiometry, as well as of the ordered B2 (FeAl, CoAl, NiAl) phases with point defects are presented. The calculations were performed using the coherent potential approximation within the Korringa-Kohn-Rostoker method (KKR-CPA) for the disordered case and the tight-binding linear muffin-tin orbital (TB-LMTO) 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 (TM) 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 >0.5.Comment: 11 pages with 9 embedded postscript figures, to be published in Phys.Rev.

Migration Aspect in the Oil-Bearing Capacity of the Domanic Formation in Tatarstan

The article highlights the problem of oil bearing of the Domanic Formation on the territory of the Republic of Tatarstan. Comparing the geochemical characteristics of bitumen of the Semilukskian horizon and oils of the Eifelian-Frasnian terrigenous complex, it was concluded that in the Semilukskian horizon, mobile bitumen are present along with the syngenetic dispersed matter, which, according to gas-liquid chromatography, are identical to the oil of the underlying terrigenous deposits of the Pashian and Timanian horizons. These bitumens are migratory and reflect the process of upward vertical oil migration, which is responsible for the formation of industrial deposits in the Semilukskian, Sargaevskian, and Rechitskian horizons in those areas where the lithological features of the rocks and the development of superficial fracturing in them make it possible to create a collecting space. The rocks of the Domanic facies should be considered as accumulation or accumulation-generation system, oil deposits of which were formed due to oil systems generated in other sources. New methods of search are needed that allow us to quickly assess the content of migratory hydrocarbons and syngenetic organic matter. This is possible on the basis of a rapid study of the sludge, which will allow to assess the presence of mobile hydrocarbons and their quantity during drilling. An analysis of the spatial distribution of migratory hydrocarbons will allow localizing oil migration channels