Showing papers by "Wolf Gero Schmidt published in 2023"
TL;DR: In this paper , the adsorption of cyclic (alkyl) (amino) carbenes on the monohydride Si(001) surface is explored within density-functional theory.
Abstract: : The adsorption of cyclic (alkyl) (amino) carbenes on the monohydride Si(001) surface is explored within density-functional theory. Two different adsorption mechanisms are investigated: the carbene insertion in Si − H bonds and the binding to a surface defect with missing hydrogen. The relative stability of these configurations depends on the hydrogen chemical potential, i.e., the surface preparation conditions as well as on the molecular side groups. The latter are also found to decisively influence the molecular diffusion. Some adsorption configurations are found to give rise to electronic states within the silicon bulk band gap. A sizable reduction of the work function is found upon molecular adsorption.
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TL;DR: Composites of different graphene oxide types, TiO2 materials, and especially synthetic routes influence the photocatalytic activity of the resulting material as mentioned in this paper , which is the case for many of the synthetic routes.
TL;DR: A series of new organic donor-π-acceptor-dyes incorporating a diquat moiety as a novel electron acceptor unit have been synthesized and characterized, and the analytical data were supported by DFT calculations as mentioned in this paper .
Abstract: A series of new organic donor-π-acceptor-dyes incorporating a diquat moiety as a novel electron-acceptor-unit have been synthesized and characterized, and the analytical data were supported by DFT calculations. These dyes have been explored in the aerobic thiocyanation of indoles and pyrroles. Here they showed a high photocatalytic activity under visible light, giving isolated yields of up to 97%.
TL;DR: In this paper , the structural, electronic and optical properties of the three main phases of TiO2 crystals have been calculated using Hubbard U correction and hybrid functional methods in density-functional theory.
Abstract: As a benchmark, the structural, electronic and optical properties of the three main phases of TiO2 crystals have been calculated using Hubbard U correction and hybrid functional methods in density-functional theory. These calculations are compared concerning the available experimental observations on pristine TiO2 crystals. Modified hybrid functionals, particularly the PBE0 functional with 11.4% fraction of exact exchange, are shown to provide highly accurate atomic structures and also accurate electronic structure data, including optical excitation energies. With DFT + U, accurate optical spectra are also possible, but only if the Hubbard U is applied on the O 2p electrons exclusively. Furthermore, both methods, the 11.4%-PBE0 hybrid functional and the DFT + U p scheme have been used to study TiO2 amorphous ultra-thin films, confirming the agreement of the two methods even with respect to small details of the optical spectra. Our results show that the proposed DFT + U p methodology is computationally efficient, but still accurate. It can be applied to well-ordered TiO2 polymorphs as well as to amorphous TiO2 and will allow for the calculations of complex titania-based structures.