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Register a new userAdsorption and dissociation of O$_{2}$ at Be(0001): First-principles prediction of an energy barrier on the adiabatic potential energy surface
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The adsorption and dissociation of O$_{2}$ molecules at the Be(0001) surface is studied by using density-functional theory within the generalized gradient approximation and a supercell approach. The physi- and chemisorbed molecular precursor states are identified to be along the parallel and vertical channels, respectively. It is shown that the HH-Z (see the text for definition) channel is the most stable channel for the molecular chemisorption of O$_{2}$. The electronic and magnetic properties of this most stable chemisorbed molecular state are studied, which shows that the electrons transfer forth and back between the spin-resolved antibonding $pi^{ast}$ molecular orbitals and the surface Be $sp$ states. A distinct covalent weight in the molecule-metal bond is also shown. The dissociation of O$_{2}$ is determined by calculating the adiabatic potential energy surfaces, wherein the T-Y channel is found to be the most stable and favorable for the dissociative adsorption of O$_{2}$. Remarkably, we predict that unlike the other simple $sp$ metal surfaces such as Al(111) and Mg(0001), the textit{adiabatic} dissociation process of O$_{2}$ at Be(0001) is an activated type with a sizeable energy barrier.
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We report first-principles calculations of acoustic surface plasmons on the (0001) surface of Be, as obtained in the random-phase approximation of many-body theory. The energy dispersion of these collective excitations has been obtained along two symmetry directions. Our results show a considerable anisotropy of acoustic surface plasmons, and underline the capability of experimental measurements of these plasmons to {it map} the electron-hole excitation spectrum of the quasi two-dimensional Shockley surface state band that is present on the Be(0001) surface.
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