Adsorption and dissociation of H2O on Zr(0001) with density-functional theory studies

Abstract

The adsorption and dissociation of isolated H 2 O molecule on Zr(0001) surface are theoretically investigated for the first time by using density-functional theory calculations. Two kinds of adsorption configurations with almost the same adsorption energy are identified as the locally stable states, i.e., the flat and upright configurations respectively. It is shown that the flat adsorption states on the top site are dominated by the 1b 1 -d band coupling, insensitive to the azimuthal orientation. The diffusion between adjacent top sites reveals that the water molecule is very mobile on the surface. For the upright configuration, we find that besides the contribution of the molecular orbitals 1b 1 and 3a 1 , the surface→water charge transfer occurring across the Fermi level also plays an important role. The dissociation of H 2 O is found to be very facile, especially for the upright configuration, in good accordance with the attainable experimental results. The present results afford to provide a guiding line for deeply understanding the water-induced surface corrosion of zirconium.

Bi-Doped Zirconium Alloys with Enhanced Water Oxidation Resistance

“…This agrees well with the previous DFT study which suggested that the lowest energy path is the bri site dissociation. 12 The structure images of the CI-NEB paths are plotted in Figures 4−6. For the bri path, the H 2 O molecule first slightly moves toward the hcp site and tilts, as shown in Figure 4a− The dissociation path of the top-f path is similar to that along the top-h path, as shown in Figure 6.…”

“…Five atomic Zr layers were adopted in the slab model with the bottom two layers fixed and the three top layers are free to relax in simulations. The five-layer model is enough to study the water dissociation mechanism on the Zr (0001) surface . A 20 Å vacuum region was applied in the slab model to avoid the interaction between replicated images.…”

“…Density functional theory (DFT) simulations provide an atomic level view of the adsorption process of water on Zr. Previous first-principles simulations by Wang et al and Nie et al . indicated that the azimuthal orientation of the flat-lying water molecule has a small effect on the adsorption energy and that the upright water configuration is more favorable for water dissociation.…”

“…Density functional theory (DFT) simulations provide an atomic level view of the adsorption process of water on Zr. Previous first-principles simulations by Wang et al 12 and Nie et al 13 indicated that the azimuthal orientation of the flat-lying water molecule has a small effect on the adsorption energy and that the upright water configuration is more favorable for water dissociation. Through computing the water absorption energy from various zirconium (Zr) doped systems, Nie et al 13 proposed that dopants, such as Ge, Sn, Sb, Zn, Ga, Ru, Rh, Pd, Ag, Cr, Mn, Fe, Co, Ni, Cu, Nb, and Mo, could be considered as promising elements to improve resistance of water oxidation.…”

“…The fivelayer model is enough to study the water dissociation mechanism on the Zr (0001) surface. 12 A 20 Å vacuum region was applied in the slab model to avoid the interaction between replicated images. The water molecule is placed on the slab, and a dipole correction is applied to compensate for the induced dipole moment.…”