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Wolf Gero Schmidt

Bio: Wolf Gero Schmidt is an academic researcher from University of Paderborn. The author has contributed to research in topics: Density functional theory & Adsorption. The author has an hindex of 46, co-authored 366 publications receiving 8281 citations. Previous affiliations of Wolf Gero Schmidt include Massey University & University of South Africa.


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TL;DR: In this article, the influence of a simple semi-empirical van der Waals (vdW) correction on the description of dispersive, covalent, and ionic bonds within density functional theory is studied.
Abstract: The influence of a simple semiempirical van der Waals (vdW) correction on the description of dispersive, covalent, and ionic bonds within density functional theory is studied. The correction is based on the asymptotic London form of dispersive forces and a damping function for each pair of atoms. It thus depends solely on the properties of the two atoms irrespective of their environment and is numerically very efficient. The correction is tested in comparison with results obtained using the generalized gradient approximation or the local density approximation for exchange and correlation. The results are also compared with reference values from experiment or quantum chemistry methods. In order to probe the universality and transferability of the semiempirical vdW correction, a range of solids and molecular systems with covalent, heteropolar, and vdW bonds are studied.

712 citations

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TL;DR: The comparison of the present calculations with measured optical response data of rutile indicate that discrepancies discussed in numerous earlier studies are due to the measurements rather than related to an insufficient theoretical description.
Abstract: In this study, we present a combined density functional theory and many-body perturbation theory study on the electronic and optical properties of TiO2 brookite as well as the tetragonal phases rutile and anatase. The electronic structure and linear optical response have been calculated from the Kohn‐Sham band structure applying (semi)local as well as nonlocal screened hybrid exchange‐correlation density functionals. Single-particle excitations are treated within the GW approximation for independent quasiparticles. For optical response calculations, two-particle excitations have been included by solving the Bethe‐Salpeter equation for Coulomb correlated electron‐hole pairs. On this methodological basis, gap data and optical spectra for the three major phases of TiO2 are provided. The common characteristics of brookite with the rutile and anatase phases, which have been discussed more comprehensively in the literature, are highlighted. Furthermore, the comparison of the present calculations with measured optical response data of rutile indicate that discrepancies discussed in numerous earlier studies are due to the measurements rather than related to an insufficient theoretical description. (Some figures may appear in colour only in the online journal)

575 citations

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TL;DR: The adsorption of adenine on graphite is analyzed from first-principles calculations as a model case for the interaction between organic molecules and chemically inert surfaces and finds no chemical bonding due to ionic or covalent interactions.
Abstract: The adsorption of adenine on graphite is analyzed from first-principles calculations as a model case for the interaction between organic molecules and chemically inert surfaces. Within density-functional theory we find no chemical bonding due to ionic or covalent interactions, only a very weak attraction at distances beyond the equilibrium position due to the lowering of the kinetic energy of the valence electrons. Electron exchange and correlation effects are much more important for the stabilization of the adsystem. They are modeled by the local density or generalized gradient approximation supplemented by the London dispersion formula for the van der Waals interaction.

260 citations

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TL;DR: In this article, a semi-empirical dispersion correction scheme (DFT-D) was proposed for the methane-graphene interaction using density functional theory complemented with an ab initio van der Waals density functional (vdW-DF) ansatz.

135 citations

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TL;DR: The effects of electron-electron and electron-hole correlations are investigated theoretically, finding that condensation leads to delocalization of the exciton onto nearby hydrogen-bonded molecules and has a dramatic impact on the line shape.
Abstract: The optical spectrum of water is not well understood For example, the main absorption peak shifts upwards by 13 eV upon condensation, which is contrary to the behavior expected from aggregation-induced broadening of molecular levels We investigate theoretically the effects of electron-electron and electron-hole correlations, finding that condensation leads to delocalization of the exciton onto nearby hydrogen-bonded molecules This reduces its binding energy and has a dramatic impact on the line shape The calculated spectrum is in excellent agreement with experiment

115 citations


Cited by
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[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

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TL;DR: It is shown that the effective atomic C6 coefficients depend strongly on the bonding environment of an atom in a molecule, and the van der Waals radii and the damping function in the C6R(-6) correction method for density-functional theory calculations.
Abstract: We present a parameter-free method for an accurate determination of long-range van der Waals interactions from mean-field electronic structure calculations. Our method relies on the summation of interatomic C6 coefficients, derived from the electron density of a molecule or solid and accurate reference data for the free atoms. The mean absolute error in the C6 coefficients is 5.5% when compared to accurate experimental values for 1225 intermolecular pairs, irrespective of the employed exchangecorrelation functional. We show that the effective atomic C6 coefficients depend strongly on the bonding environment of an atom in a molecule. Finally, we analyze the van der Waals radii and the damping function in the C6R � 6 correction method for density-functional theory calculations.

4,825 citations

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TL;DR: This review acquaints some materials for performing OER activity, in which the metal oxide materials build the basis of OER mechanism while non-oxide materials exhibit greatly promising performance toward overall water-splitting.
Abstract: There is still an ongoing effort to search for sustainable, clean and highly efficient energy generation to satisfy the energy needs of modern society. Among various advanced technologies, electrocatalysis for the oxygen evolution reaction (OER) plays a key role and numerous new electrocatalysts have been developed to improve the efficiency of gas evolution. Along the way, enormous effort has been devoted to finding high-performance electrocatalysts, which has also stimulated the invention of new techniques to investigate the properties of materials or the fundamental mechanism of the OER. This accumulated knowledge not only establishes the foundation of the mechanism of the OER, but also points out the important criteria for a good electrocatalyst based on a variety of studies. Even though it may be difficult to include all cases, the aim of this review is to inspect the current progress and offer a comprehensive insight toward the OER. This review begins with examining the theoretical principles of electrode kinetics and some measurement criteria for achieving a fair evaluation among the catalysts. The second part of this review acquaints some materials for performing OER activity, in which the metal oxide materials build the basis of OER mechanism while non-oxide materials exhibit greatly promising performance toward overall water-splitting. Attention of this review is also paid to in situ approaches to electrocatalytic behavior during OER, and this information is crucial and can provide efficient strategies to design perfect electrocatalysts for OER. Finally, the OER mechanism from the perspective of both recent experimental and theoretical investigations is discussed, as well as probable strategies for improving OER performance with regards to future developments.

3,976 citations