Symmetry-mediated ${\mathrm{H}}_{2}\mathrm{O}$ diffusion on Al{100}

Symmetry-mediated $H_{2} O$ diffusion on Al{100}

Jibiao Li, Ying Li, Shenglong Zhu, and Fuhui Wang

Phys. Rev. B 74, 153415 – Published 25 October 2006

Abstract

Based upon the full-electron ab initio calculations, we found orientational preferences and correlation for the atop-to-atop motions of an $H_{2} O$ on Al{100}, which originates from the symmetry match between an $H_{2} O$ and the surface square lattice. We have provided theoretical evidence that the favored mechanisms can be classical hopping coupled with either the molecular flipping or in-plane reorientations, with reduced energy barriers compared to those of the simple translational motions; while quantum tunneling assisted motion is not favored for an $H_{2} O$ via the nearest neighbor diffusion.

Received 19 June 2006

DOI:https://doi.org/10.1103/PhysRevB.74.153415

Authors & Affiliations

Jibiao Li^*, Ying Li, Shenglong Zhu, and Fuhui Wang^*

State Key Laboratory for Corrosion and Protection, Institute of Metal Research (IMR), Chinese Academy of Sciences, 62 Wencui Road, Shenyang 110015, People’s Republic of China

^*Author to whom correspondence should be addressed. Electronic address: jibiaoli@imr.ac.cn, fhwang@imr.ac.cn

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Vol. 74, Iss. 15 — 15 October 2006

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Figure 1
(Color online) (a) Schematic diagram of the atop-to-atop motions for an $H_{2} O$ on Al{100}. The two types of the obtained stable structures ( $α$ and $β$ ) were used as the initial and final states, and the corresponding azimuths ( $ω_{i}$ and $ω_{f}$ ) are defined as the angle between the twofold molecular axis and the atop-to-atop direction. The diffusion paths are denoted as the combinations $P (ω_{i}, ω_{f})$ , where $ω_{i}$ , $ω_{f} ∊ {0, \pm π ∕ 2, π; \pm π ∕ 4, \pm 3 π ∕ 4}$ . The investigated diffusion paths $P (ω_{i}, ω_{f})$ are shown in (b) to (e), and the arrows stand for jump directions. The energy barriers $E (ω_{i}, ω_{f})$ are listed in the Table .Reuse & Permissions
Figure 2
(Color online) The contour map for activation energy $E (ω_{i}, ω_{f})$ of atop-to-atop diffusions $P (ω_{i}, ω_{f})$ . $E (ω_{i}, ω_{f})$ fluctuates periodically in the energy range of $[0.17 - 0.38] eV$ . The minima $(0.17 eV)$ , $E (0, 0)$ , $E (π, π)$ , and $E (π, 0)$ , are for diffusion modes of simple hopping $(H)$ and flipping $(F)$ respectively as shown in Fig. 3; while the maxima $(0.38 eV)$ are located at $E (π ∕ 2, - π ∕ 2)$ and $E (- π ∕ 2, π ∕ 2)$ . The dashed mesh is related to barriers of the diffusion paths shown in Figs. 1b to 1e, and the azimuths are extended to $2 π$ to get a whole view of each minimum.Reuse & Permissions
Figure 3
(Color online) The candidate molecular mechanisms for the atop-to-atop motions of an $H_{2} O$ on Al{100} (side view). (a) flipping mode for diffusion; (b) rotation mode for diffusion; the two modes are considered as the action of simple hopping concerted with molecule flipping or frustrated rotation; (c) NEB determined energy curves for the diffusion modes of simple hopping $P (0, 0)$ , molecular flipping $P (π, 0)$ , and $P (0, π)$ . The energy profile for lateral translation $\underset{̱}{P} (0, 0)$ is shown for comparison. The star $(*)$ marks the relative equilibrium energy of the monomer over the bridge site, with respect to that of the stable structures at atop site.Reuse & Permissions
Figure 4
(Color online) Azimuthal transitions in the course of the lateral hopping motion. a) The contour map of relative energy distribution as a function of azimuth and coordinate of the monomer in the atop-to-atop diffusions. Energy step of the contour lines has the value of $0.02 eV$ , and several energy values of the lines are shown. The map is constructed from series of path $P (ω_{i}, ω_{f})$ within the lowest energy region $∣ ω_{i} ∣ + ∣ ω_{f} ∣ < π ∕ 4$ in Fig. 2, where $ω$ varies from $- π ∕ 4$ to $π ∕ 4$ . (b) Projected energy surface of the selected region in map (a).Reuse & Permissions

Physical Review B

covering condensed matter and materials physics

Symmetry-mediated $H_{2} O$ diffusion on Al{100}

Jibiao Li, Ying Li, Shenglong Zhu, and Fuhui Wang

Phys. Rev. B 74, 153415 – Published 25 October 2006

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Physical Review B

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Symmetry-mediated H2O diffusion on Al{100}

Jibiao Li, Ying Li, Shenglong Zhu, and Fuhui Wang

Phys. Rev. B 74, 153415 – Published 25 October 2006

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Symmetry-mediated $H_{2} O$ diffusion on Al{100}