Density Functional Theory Study of H2, O2, N2, and Nh3 Adsorption Onto Zr(0001) Surfaces

Abstract

The design of corrosion resistant zirconium alloys in the nuclear industry is of great academic as well as practical significance. During corrosion of zirconium alloys at elevated temperature in the reactors, the hydrogen uptake occurs to degrade the mechanical properties inevitably. The present study addresses the poorly understood adsorption behavior of gas products of nitrogen-containing reducing coolant by applying DFT to investigate the adsorption of H2, O2, N2, and NH3 on Zr(0001) surfaces. The accumulation of these gases has a profound effect on the corrosion resistance of zirconium alloy. The studies demonstrate that the adsorption capacities of Zr(0001) surfaces decrease in the order of O2 > N2 > NH3 > H2. The adsorption processes involved are also characterized based on density of states calculations. The calculations demonstrate that strongly overlapping O 2p, N 2p, and Zr 4p and 4d states result in the chemisorption of O2, N2, and NH3 species on Zr(0001) surfaces, while these states do not overlap strongly for H2, resulting in its physisorption. The NH3 and N2 compounds can prevent hydrogen uptake on zirconium alloy surfaces to some extent because they are more preferentially adsorbed on the Zr(0001) surface than H2.

Keywords: Zr(0001) surfaces, Density functional theory, Hydrogen uptake