Oxygen Atom Adsorption on and Diffusion into Nb(110) and Nb(100) from First Principles

Journal Article · Fri Nov 01 04:00:00 EDT 2013 · JOM

DOI:https://doi.org/10.1007/s11837-013-0735-8· OSTI ID:1129496

Tafen, De Nyago; Gao, Michael C

In order to understand the dynamics of oxidation of Nb, we examine the adsorption, absorption, and diffusion of an oxygen atom on, in, and into Nb(110) and Nb(100) surfaces, respectively, using density functional theory. Our calculations predict that the oxygen atom adsorbs on the threefold site on Nb(110) and the fourfold hollow site on Nb(100), and the adsorption energy is -5.08 and -5.18 eV respectively. We find the long and short bridge sites to be transition states for O diffusion on Nb(110), while the on top site is a rank-2 saddle point. In the subsurface region, the oxygen atom prefers the octahedral site, as in bulk niobium. Our results also show that the O atom is more stable on Nb(110) subsurface than on Nb(100) subsurface. The diffusion of oxygen atoms into niobium surfaces passes through transition states where the oxygen atom is coordinated to four niobium atoms. The diffusion barriers of the oxygen atom into Nb(110) and Nb(100) are 1.81 and 2.05 eV, respectively. Analysis of the electronic density of states reveals the emergence of well localized electronic states below the lowest states of clean Nb surfaces due to d-p orbital hybridization.

• Research Organization: National Energy Technology Laboratory - In-house Research
• Sponsoring Organization: USDOE Office of Fossil Energy (FE)
• DOE Contract Number: FE0004000
• OSTI ID: 1129496
• Report Number(s): A-CONTR-PUB-016
• Journal Information: JOM, Journal Name: JOM Journal Issue: 11 Vol. 65
• Country of Publication: United States
• Language: English

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36 MATERIALS SCIENCE