Mg(0001) surface oxidation: A two-dimensional oxide phase

Abstract

First-principles electronic structure calculations and angle-scanned x-ray photoelectron diffraction experiments reveal the geometrical structure of the Mg͑0001͒ surface upon oxidation. In contrast to previous studies of Mg͑0001͒ oxidation and unlike the case of aluminum oxidation we determine a surface oxide structure, consisting of mixed oxygen-magnesium layers on top of an almost unchanged Mg͑0001͒ surface. This unusual, directionally bound, surface oxide is locally formed already at very low dosing, corresponding to total coverages of 0.1 monolayer ͑ML͒, and grows laterally with increasing oxygen coverage up to at least 3 ML total coverage.

First-principles insights into the structure of the incipient magnesium oxide and its instability to decomposition: Oxygen chemisorption to Mg(0001) and thermodynamic stability

“…8 X-ray photoelectron diffraction (XPD) measurements, single scattering cluster (SSC) formalism, and DFT studies have been used to study the oxide structure that evolved from Mg(0001). [43][44][45] This XPD-SSC-DFT study was unable to deduce the precise structure of the low-exposure incipient oxide phase, but they did comment that it had "the same" local geometry as the higher-exposure structures, which were characterized as "flat" and MgO(111)-like 43-45 -the oxygen atoms were approximately in-plane with the magnesium atoms raised from the tetrahedral-1 positions. Work-function experiments of Mg(0001) with increasing oxygen exposure have been performed.…”

“…43,44 Schröder, Fasel, and Kiejna used x-ray photoelectron diffraction (XPD) measurements, single scattering cluster (SSC) formalism, 45 and DFT to study the oxide structure that evolved from Mg(0001) exposures of 0.15, 1.4, and 8.7 L. Here, DFT was used to find the structure of possible monolayer and multilayer oxide structures; 39,40 SSC was used to simulate the XPD behavior of these DFT determined structures. They found that the multilayered oxide was a mixed 2and 3-ML structure on top of an almost undistorted Mg(0001) surface and had a graphite-like structure.…”

“…In this paper and the previous work by Schröder, Fasel, and Kiejna,43,44 experimental data combined with theoretical analysis has been used to ascribe atomic-scale structure to observation. The structural space sampled between these two datasets may not be considered to be exhaustive, but may be considered to be somewhat representative as they have been correlated with experimentation.…”

“…With increasing agglomeration these clusters grow and eventually undergo spinodal decomposition to form clusters of multilayer oxide. 8,25,26,43,44 Subsequent dissociative chemisorption of O 2 results in the preferential growth of the multilayer oxide rather than the renewal of clusters. Those clusters which transformed into multilayer oxide will act as oxide nuclei and agglomeration sites until the oxide growth process is complete.…”

THE OXIDATION OF NIAL: What Can We Learn from Ab Initio Calculations?

“…Comparison of the errors (in meV per oxygen atom) generated if one assumes that total energies at 0 K approximate either enthalpies (Method H) or Gibbs free energies (Method G) of crystalline oxide A n O m and oxide-forming element A in Equation(17). The errors are calculated as [ h 0…”