Computer simulation of defects and reactions at oxide surfaces

Colbourn, E.A.

doi:10.1016/0167-5729(92)90013-2

Cited by 167 publications

(48 citation statements)

References 128 publications

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“…We limit our study to two surface planes: MgO (100) and hydroxylated MgO (111). While the MgO (100) surface is the most stable surface under dry conditions, 20 configuration than (100) in aqueous conditions. 21 In spite of the instability of the pure polar MgO (111), its hydroxyl saturation reduces the surface dipole by several eV [22][23][24] thus minimizing the surface energy.…”

mentioning

confidence: 99%

Communication: Band bending at the interface in polyethylene-MgO nanocomposite dielectric

Kubyshkina

Unge

Jonsson

2017

The Journal of Chemical Physics

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mentioning

confidence: 99%

Communication: Band bending at the interface in polyethylene-MgO nanocomposite dielectric

Kubyshkina

Unge

Jonsson

2017

The Journal of Chemical Physics

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“…MgO has the cubic rocksalt structure with (001) cleavage planes. This is the most stable surface and is the only one seen experimentally 6 . The simplest possibility for a hydroxylated surface is obtained by dissociating a water molecule and placing the OH group above each magnesium ion and the H above each oxygen of the (001) surface (see Fig.…”

mentioning

confidence: 99%

Water chemisorption and reconstruction of the MgO surface

Refson¹,

Wogelius²,

Fraser³

et al. 1995

Phys. Rev. B

244

158

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The observed reactivity of MgO with water is in apparent conflict with theoretical calculations which show that molecular dissociation does not occur on a perfect (001) surface. We have performed ab-initio total energy calculations which show that a chemisorption reaction involving a reconstruction to form a (111) hydroxyl surface is strongly preferred with ∆E = −90.2 kJ mol −1 . We conclude that protonation stabilizes the otherwise unstable (111) Magnesium oxide has long provided a prototype for the study of surface structure and chemical reactions of oxides. Naturally occurring MgO, known by its mineral name of periclase, is not a common crustal mineral, but its simple structure makes it an excellent example for the investigation of mineral surface chemistry.Reactions at mineral surfaces are responsible for much of the chemical change which occurs in the Earth's crust. Weathering reactions control the erosion of rocks and the consequent evolution of surface topography thus providing an opposing mechanism to the more dramatic process of mountain building. Aqueous reactions in sedimentary basins are responsible for the diagenetic processes which transform unconsolidated sediments into rocks. In this work we study the nature of a simple mineral surface when exposed to an aqueous environment and the chemical interaction of water with that surface. This is both a prerequisite to studying the interaction with aqueous solutions and a tractable first step towards ligand-exchange reactions in more complex silicate minerals.We have performed experiments on single-crystals of MgO prepared with high-quality (001) faces which were reacted with acidic solutions. The experiments and results are reported in detail elsewhere 1 , the main feature being the development of an altered surface layer. Elastic Recoil Detection Analysis (ERDA)2 shows protonation to a depth of 900Å with a H/Mg ratio close to 2 giving a probable chemical composition of magnesium hydroxide. Indeed brucite (the mineralogical name for Mg(OH) 2 ) is the most common alteration product of periclase in the natural environment 4 and well-crystallized intergrowths of brucite on periclase have been reported 5 . The initial stage in the reaction is hydroxylation of the surface. MgO has the cubic rocksalt structure with (001) cleavage planes. This is the most stable surface and is the only one seen experimentally 6 . The simplest possibility for a hydroxylated surface is obtained by dissociating a water molecule and placing the OH group above each magnesium ion and the H above each oxygen of the (001) surface (see Fig. 1a) as postulated by Coluccia et al.7 . Some striking hydroxylation experiments were reported by Jones et al. who studied surface roughening on (001) faces of nanocrystalline MgO in a transmission electron microscope 8 . The remarkable affinity of MgO for water is demonstrated by their in situ observation of hydration-induced surface roughening over 10 minutes under vacuum with P H 2 O < 10 −5 Pa. The presence of surface hydroxyl groups on MgO powde...

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“…We use n' = 7 [I51 and the direct summation over 960 ions shows a sufficient convergence of U compared with a value reported by Johnson [17]. To sim- In this first approximation, we do not consider differences in the ionicity of the surface as compared to bulk ions in spite of the fact that this may occur in transition metal oxides [18]. For the motion of Pt2(4)+ ions along the (1 10)-direction (i.e.…”

Section: Charge Transfermentioning

confidence: 90%

Solid/gas‐interactions of Surface‐doped Oxides: C—V, I—V, XPS, UPS, and ELS Studies on Pt/TiO₂ and Pd/SnO₂ (110)

Schierbaum

Göpel

1993

Ber Bunsenges Phys Chem

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Catalysis I Electrical Properties I Interfaces I Spectroscopy, Photoelectron I SurfacesWe have investigated Pt and Pd overlayers in the submono-, mono-, and multilayer coverage range on TiOz and Sn02( 1 10)-single crystal surfaces. The interaction with O2 was studied at temperatures between 300 and 1070 K in-situ with current-and capacitance-voltage (I-V and C-V) measurements, X-ray and ultraviolet photoelectron spectroscopies (XPS and UPS), and electron energy loss spectroscopy (ELS). Under oxidizing conditions, Pt and Pd ions are formed which diffuse into the oxide substrate thereby forming Pd-acceptor and Pt-donor type bulk defects. For multilayer coverages of Pt and Pd the electrical conduction across the metauoxide interface changes drastically from Schottky diode to ohmic behaviour upon oxidation. Under reducing UHV conditions at temperatures T 2 700 K we observe the formation of neutral Pd at the Sn02 surface. Total energy calculations of TiOz with incorporated Pt2(4)f ions at different lattice positions confirm the experimentally observed fast diffusion of Pt atoms between surface, subsurface, and bulk sites.

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Computer simulation of defects and reactions at oxide surfaces

Cited by 167 publications

References 128 publications

Communication: Band bending at the interface in polyethylene-MgO nanocomposite dielectric

Communication: Band bending at the interface in polyethylene-MgO nanocomposite dielectric

Water chemisorption and reconstruction of the MgO surface

Solid/gas‐interactions of Surface‐doped Oxides: C—V, I—V, XPS, UPS, and ELS Studies on Pt/TiO₂ and Pd/SnO₂ (110)

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Computer simulation of defects and reactions at oxide surfaces

Cited by 167 publications

References 128 publications

Communication: Band bending at the interface in polyethylene-MgO nanocomposite dielectric

Communication: Band bending at the interface in polyethylene-MgO nanocomposite dielectric

Water chemisorption and reconstruction of the MgO surface

Solid/gas‐interactions of Surface‐doped Oxides: C—V, I—V, XPS, UPS, and ELS Studies on Pt/TiO2 and Pd/SnO2 (110)

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Solid/gas‐interactions of Surface‐doped Oxides: C—V, I—V, XPS, UPS, and ELS Studies on Pt/TiO₂ and Pd/SnO₂ (110)