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First principles investigation of helium physisorption on an ¿-Al2O3(0001) surface.

Journal Article


Abstract


  • The interaction of helium with an α-Al2O3(0001) surface was studied by density functional theory (DFT), with consideration of the effects of He-coverage, surface defects, He-coadsorption and van der Waals interaction, respectively. Adsorption energies of helium atoms are very small as expected for a physisorbed state, varying from -20 to -5 meV, which is attributed to the small overlap between Al 3sp, O 2sp and He 1s states. A correlation is obtained for the adsorption energies and the He to nearest-neighbor Al atom distances on a clean (0001) surface. The He atom prefers to bound atop the Al site of the fourth atomic layer (Al4 hollow site), and the favorable site around an O-vacancy is atop the site of the O vacancy with less stability. The competition between O-He attraction and Al-He repulsion makes the He stable sites. As He-coverage on the surface increases, He atoms tend to form clusters, and coadsorption configuration is not solely determined by the most stable site but also by the He-He distance. The two co-adsorbed He atoms absorb on hollow sites Al4 and Al3, with a He-He distance of 2.767 Å. The OBS dispersion corrected DFT energies are 2.2-4.4 times larger than the non-corrected DFT values and He-surface distances are smaller. Finally, implications on H/He interaction within α-Al2O3 as a tritium permeation barrier are discussed.

Publication Date


  • 2016

Citation


  • Zhang, G., Xiang, X., Yang, F., Liu, L., Tang, T., Shi, Y., & Wang, X. (2016). First principles investigation of helium physisorption on an ¿-Al2O3(0001) surface.. Physical chemistry chemical physics : PCCP, 18(23), 15711-15718. doi:10.1039/c6cp01517d

Web Of Science Accession Number


Start Page


  • 15711

End Page


  • 15718

Volume


  • 18

Issue


  • 23

Abstract


  • The interaction of helium with an α-Al2O3(0001) surface was studied by density functional theory (DFT), with consideration of the effects of He-coverage, surface defects, He-coadsorption and van der Waals interaction, respectively. Adsorption energies of helium atoms are very small as expected for a physisorbed state, varying from -20 to -5 meV, which is attributed to the small overlap between Al 3sp, O 2sp and He 1s states. A correlation is obtained for the adsorption energies and the He to nearest-neighbor Al atom distances on a clean (0001) surface. The He atom prefers to bound atop the Al site of the fourth atomic layer (Al4 hollow site), and the favorable site around an O-vacancy is atop the site of the O vacancy with less stability. The competition between O-He attraction and Al-He repulsion makes the He stable sites. As He-coverage on the surface increases, He atoms tend to form clusters, and coadsorption configuration is not solely determined by the most stable site but also by the He-He distance. The two co-adsorbed He atoms absorb on hollow sites Al4 and Al3, with a He-He distance of 2.767 Å. The OBS dispersion corrected DFT energies are 2.2-4.4 times larger than the non-corrected DFT values and He-surface distances are smaller. Finally, implications on H/He interaction within α-Al2O3 as a tritium permeation barrier are discussed.

Publication Date


  • 2016

Citation


  • Zhang, G., Xiang, X., Yang, F., Liu, L., Tang, T., Shi, Y., & Wang, X. (2016). First principles investigation of helium physisorption on an ¿-Al2O3(0001) surface.. Physical chemistry chemical physics : PCCP, 18(23), 15711-15718. doi:10.1039/c6cp01517d

Web Of Science Accession Number


Start Page


  • 15711

End Page


  • 15718

Volume


  • 18

Issue


  • 23