Hydrogen adsorption, dissociation and diffusion on the α-U(001) surface

Abstract

First-principles pseudopotential plane-wave calculations based on density functional theory and the generalized-gradient approximation have been used to study the adsorption, dissociation, and diffusion of hydrogen on the α-U(001) surface. Weak molecular chemisorption was observed for H 2 approaching with its molecular axis parallel to the surface. The optimization of the adsorption geometries on the threefold hollow sites yields final configurations with H 2 molecules moving towards the top site at both coverages considered, 0.25 and 0.5 monolayers. A low dissociation barrier of 0.081 eV was determined for H 2 dissociated from the onefold top site with the H atoms falling into the two adjacent threefold hollow sites. The analysis of the density of states along the dissociation paths shows that the hybridization of U 5f and H 1s states only occurs when the H 2 molecule is dissociated.

Density functional study of H2 molecule and H atom adsorption on α‐U(001) surface

“…This phenomenon ascribes that the interaction of H 2 with the surface on the top site is much smaller than the other three adsorption configurations. This result is consistent with the adsorption energies of H 2 molecule on U(001) surface . In the same adsorption configurations, the d 12 has much larger shrinkage than the d 23 because of the immediate interaction of H 2 molecule with the surface uranium atoms, which strengthens the interaction between the surface and subsurface, and this finally narrows the distances between all the uranium layers.…”

“…[10] Nie investigated on the adsorption, dissociation, and diffusion of H 2 on the α-U(001) surface by DFT calculations. [11] Nie's research showed that the hybridization of U 5f and H 1s state only occurs when the H 2 molecule is dissociated, which is different from our work. The different research results can be due to the improved calculations by DFT in the latter.…”

“…Taylor analyzed the binding energies, geometries, charges, and electronic structures of a series of impurity atoms [H‐Ar] interacting with the α‐U lattice by DFT calculations . Nie investigated on the adsorption, dissociation, and diffusion of H 2 on the α ‐U(001) surface by DFT calculations . Nie's research showed that the hybridization of U 5f and H 1s state only occurs when the H 2 molecule is dissociated, which is different from our work.…”

“…This result is consistent with the adsorption energies of H 2 molecule on U(001) surface. [11] In the same adsorption configurations, the d 12 has much larger shrinkage than the d 23 because of the immediate interaction of H 2 molecule with the surface uranium atoms, which strengthens the interaction between the surface and subsurface, and this finally narrows the distances between all the uranium layers. Furthermore, this phenomenon is consistent with other surface slab calculations performed for hydride surface in literatures.…”

First-Principles Study of Properties of Alpha Uranium Crystal and Seven Alpha Uranium Surfaces

“…Uranium easily reacts with hydrogen [8], oxygen [9], and water [10] due to its lively chemical nature. These reactions take place on the surface and are mainly determined by the nature of the 5f electrons of the surface atoms.…”