Segregation of sp-impurities at grain boundaries and surfaces: comparison of fcc cobalt and nickel

0481166 - ÚFM 2018 RIV GB eng J - Článek v odborném periodiku
Všianská, Monika - Vémolová, H. - Šob, Mojmír
Segregation of sp-impurities at grain boundaries and surfaces: comparison of fcc cobalt and nickel.
Modelling and Simulation in Materials Science and Engineering. Roč. 25, č. 8 (2017), č. článku 085004. ISSN 0965-0393. E-ISSN 1361-651X
Grant CEP: GA ČR(CZ) GA16-24711S
Institucionální podpora: RVO:68081723
Klíčová slova: local magnetic-moments * total-energy calculations * augmented-wave method * solute segregation * tilt boundaries * embrittling potency * alloying elements * hcp metals * basis-set * 1st-principles * grain boundary segregation * strengthening/embrittling energy * grain boundary magnetism * ab initio calculations * surface segregation
Obor OECD: Condensed matter physics (including formerly solid state physics, supercond.)
Impakt faktor: 1.793, rok: 2017

We perform systematic ab initio investigations of the segregation of 12 nonmagnetic sp-impurities (Al, Si, P, S, Ga, Ge, As, Se, In, Sn, Sb and Te) at the Sigma 5 (210) grain boundary (GB) and (210) free surface (FS) in fcc ferromagnetic cobalt and analyse their effect on structural, magnetic and mechanical properties, the results are compared with those obtained previously for nickel. It turns out that there is a slight enhancement of magnetization at the clean GB and FS with respect to bulk cobalt (4.7% and 17%, respectively). However, segregated sp-impurities sharply reduce this magnetization. As shown previously, in nickel most of the above impurities nearly destroy or substantially reduce the magnetic moments at the FS and, when segregated interstitially (i.e. Si, P, S, Ge, As, and Se), also at the GB, so that they provide atomically thin, magnetically dead layers, which may be very desirable in spintronics. The reduction of magnetic moments at the Sigma 5(210) GB in fcc ferromagnetic cobalt is, in absolute values, very similar to that in nickel. However, as the magnetic moment in bulk cobalt is higher, we do not observe magnetically dead layers here. Further, we find the preferred segregation sites at the Sigma 5(210) GB for the sp-impurities studied, and their segregation enthalpies and strengthening/embrittling energies with their decomposition into their chemical and mechanical components. It turns out that interstitially segregated Si is a GB cohesion enhancer, and interstitially segregated P, S, Ge, As, and Se and substitutionally segregated Al, Ga, In, Sn, Sb and Te are GB embrittlers in fcc cobalt. As there is essentially no experimental information on GB segregation in cobalt, most of the present results are theoretical predictions which may motivate future experimental work.
Trvalý link: http://hdl.handle.net/11104/0276769