Morphological Features and Band Bending at Nonpolar Surfaces of ZnO

We employ hybrid density functional calculations to analyze the structure and stability of the (101̅0) and (112̅0) ZnO surfaces, confirming the relative stability of the two surfaces. We then examine morphological features, including steps, dimer vacancies, and grooves, at the main nonpolar ZnO surface using density functional methods. Calculations explain why steps are common on the (101̅0) surface even at room temperature, as seen in experiment. The surface structure established has been used to obtain the definitive ionization potential and electron affinity of ZnO in good agreement with experiment. The band bending across the surface is analyzed by the decomposition of the density of states for each atomic layer. The upward surface band bending at the (101̅0) surface affects mostly the valence band by 0.32 eV, which results in the surface band gap closing by 0.31 eV; at the (112̅0) surface, the valence band remains flat and the conduction band bends up by 0.18 eV opening the surface band gap by 0.12 eV

Real and virtual polymorphism of titanium selenide with robust interatomic potentials

The first successful pairwise potential for a layered material, TiSe2, has been parameterised to fit the experimental data, using a genetic algorithm as the optimisation tool for the parameters of the interatomic potential. This potential has been tested on a wide range of hypothetical isomorphous AX2 metastable phases using ab initio derived data. From the initial survey, the ground state 1T–TiSe2 structure remains the lowest enthalpy phase in a wide range of pressures (0 to 25 GPa), which leaves open questions about the nature of a reported unknown high-pressure phase

The nature of the molybdenum surface in iron molybdate. The active phase in selective methanol oxidation

The surface structure of iron molybdate is of greatsignificance since this is the industrial catalyst for the direct selective oxidation of methanol to formaldehyde. There is a debate concerning whether Fe2(MoO4)3 acts as a benign support for segregated MoO3 or if there is an intrinsic property of the surface structure whichfacilitates its high catalytic efficacy. This study provides new insights into the structure of this catalyst, identifying a bound terminating layer of octahedral Mo units as the active and selective phase. Here we examine whether only 1 monolayer of Mo on iron oxide alone isefficacious for this reaction. For a 1 ML MoOx shell?Fe2O3 core catalyst the Mo remains at the surface under all calcination procedures while exhibiting high selectivity and activity. The work highlights how catalyst surfaces are significantly different from bulk structures and this difference is crucial for catalyst performance