Anisotropic thermal displacements of adsorbed atoms and molecules on surfaces studied by low-energy electron diffraction

Two-Way Twisting of a Confined Monolayer: Orientational Ordering within the van der Waals Gap between Graphene and Its Crystalline Substrate

Two-dimensional confinement of lattices produces a variety of order and disorder phenomena. When the confining walls have atomic granularity, unique structural phases are expected, of relevance in nanotribology, porous materials, or intercalation compounds where, e.g., electronic states can emerge accordingly. The interlayer's own order is frustrated by the competing interactions exerted by the two confining surfaces. We revisit the concept of orientational ordering, introduced by Novaco and McTague to describe the twist of incommensurate monolayers on crystalline surfaces. We predict a two-way twist of the monolayer as its density increases. We discover such a behavior in alkali atom monolayers (sodium, cesium) confined between graphene and an iridium surface, using scanning tunneling microscopy and electron diffraction.

NO Binding Energies to and Diffusion Barrier on Pd Obtained with Velocity-Resolved Kinetics

We report nitric oxide (NO) desorption rates from Pd(111) and Pd(332) surfaces measured with velocity-resolved kinetics. The desorption rates at the surface temperatures from 620 to 800 K span more than 3 orders of magnitude, and competing processes, like dissociation, are absent. Applying transition state theory (TST) to model experimental data leads to the NO binding energy E ₀ = 1.766 ± 0.024 eV and diffusion barrier D _T = 0.29 ± 0.11 eV on the (111) terrace and the stabilization energy for (110)-steps ΔE _ST = 0.060_-0.030 ^+0.015 eV. These parameters provide valuable benchmarks for theory.

An ab initio molecular dynamics study of D2 dissociation on CO-precovered Ru(0001)

In dynamics studies of hydrogen dissociation on CO pre-covered Ru(0001) the simulation cell size is important for describing energy exchange.

The structure of carbon monoxide adsorbed on the NaCl(100) surface—a combined LEED and DFT-D/vdW-DF study

The structure of the first layer CO adsorbed on NaCl(100) is investigated experimentally by means of quantitative low-energy electron diffraction at 25 K, and theoretically by means of density functional theory. Consistent with earlier helium atom diffraction results, the monolayer structure has p(2×1) symmetry with a glide-plane along the longer axis of the unit cell. The structure analysis confirms the binding of CO via the carbon end to the NaCl(100) surface. The vertical distance of carbon above Na(+) is 2.58 ± 0.08 Å, in good agreement with geometry optimizations based on dispersion-corrected density functional theory, and 0.15 Å lower than predicted in calculations based on the nonlocal van der Waals density functional.