Understanding Cr segregation at the He bubble surface in Fe.
Although Cr segregation at the free Fe surface is weak, noticeable segregation of Cr at the He bubble surface in Fe has recently been observed. To understand the driving force for Cr segregation, we have carried out first-principles density functional theory calculations on the energetics of solute Cr atoms at the He bubble surface, which was modeled by a Fe/He interface. We find that both the compressive stress produced by the He bubble and the direct interfacial interaction promote Cr segregation from inside the bulk to the bubble surface, along with reduced spin polarization. Electronic structure analyses show that at the Fe/He interface, Cr is more compressible than Fe due to having more empty e(g) orbitals and, accordingly, the Fe surface gets energetically more favorable for Cr than in the bulk. On the other hand, the segregation of Cr increases the charge density at the bubble surface, and thus hinders assimilation of further He atoms.
School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, People's Republic of China.
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Geng
D002857:Chromium / Q000737:chemistry*; D006371:Helium / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D008956:Models, Chemical; D013499:Surface Properties
D002857:Chromium; D006371:Helium; D007501:Iron