Electronic structure of the c(4×2) reconstructed Ge(001) surface

Adsorption of Homotrifunctional 1,2,3-Benzenetriol on a Ge(100)-2 × 1 Surface

The adsorption of the homotrifunctional 1,2,3-benzenetriol on Ge(100)-2 × 1 has been investigated by density functional theory calculations, Fourier transform infrared spectroscopy, and X-ray-photoelectron spectroscopy. The results show that the adsorption can occur through OH dissociation of all three hydroxyl groups, and that all three reaction pathways are kinetically and thermodynamically favorable. A coverage-dependent analysis shows that at low coverage, the molecule reacts to form a mix of trifold and dually bound adsorbates. As the coverage increases, the reactions are limited to dissociative adsorption through single and dual attachments. Calculations on the three possible dually bound configurations further reveals that the dissociative adsorption of the third hydroxyl group is limited by geometrical constraints to only two reaction channels. Finally, the proximity between OH-groups in the molecule favors intra- and intermolecular hydrogen bonding, which stabilizes singly and dually bound adsorbate configurations and limits the reactivity of the functional groups.

An improved density functional theory description of the Ge(100)c(4×2) surface using the MBJLDA xc potential and spin-orbit interactions

The MBJLDA xc potential (modified Becke-Johnson exchange potential with local density approximation correlation) proposed by Tran and Blaha has been designed and shown to significantly improve the description of the fundamental energy gaps of a wide range of bulk materials. Recently we reported that combining this MBJLDA xc potential with spin-orbit interactions and local density approximation pseudopotentials within the plane wave density functional method led to results for bulk germanium that were at least as accurate as those obtained from far more sophisticated and computationally expensive methods such as the GW method. Here we demonstrate that the application of this approach to the Ge(100)c(4×2) surface yields results that are in excellent agreement with the available experimental data.

The origin of the pseudogap in α-Ga

Density functional theory, the free-electron empty lattice approximation and the nearly free-electron approximation are employed to investigate the electronic properties of partially covalent α-Ga. Whereas free-electron-like properties are revealed over a large energy range, a deep pseudogap at the Fermi level is characteristic of α-Ga. We explain the origin of the pseudogap in terms of a delicate interplay between the electronic states and the specific Brillouin zone geometry.

First-principles calculations of electronic states and self-doping effects at a 45 degrees grain boundary in the high temperature YBa2Cu3O7 superconductor

The charge redistribution at grain boundaries determines the applicability of high-T_{c} superconductors in electronic devices because the transport across the grains can be hindered considerably. We investigate the local charge transfer and the modification of the electronic states in the vicinity of the grain-grain interface by ab initio calculations for a (normal-state) 45 degrees -tilted [001] grain boundary in YBa2Cu3O7. Our results explain the suppressed interface transport and the influence of grain boundary doping in a quantitative manner, in accordance with the experimental situation. The charge redistribution is found to be strongly inhomogeneous, which has a substantial effect on transport properties since it gives rise to a self-doping of 0.10+/-0.02 holes per Cu atom.