arXiv subjects

Wolfgang Moritz

Publications and source records attributed to Wolfgang Moritz.

4 recordsLinked to original sources

arXiv2021

Low-Energy Electron Diffraction With Energy Invariant Carrier Wave Wavenumber Modulated by Exchange-Correlation Interaction

We present low-energy electron diffraction (LEED) as elastic electron-atom scattering (EEAS) operating in a target crystal waveguide where a Coulombic carrier wave is wavenumber modulated by exchange-correlation (XC) interaction. Carrier potential is designed using a KKR (Korringa-Kohn-Rostoker) muffin-tin model built on overlapping free atoms. XC potential is constructed using Sernelius's many-particle theory on electron self-energy. EEAS phase shifts are derived from Dirac's differential equations, and four recent LEED investigations are recalculated: Cu(111)+$( 3\!\surd3\times\!\surd3 ) \mathrm{R30^\circ}$-TMB, Ag(111)+$(4\!\times \!4 )$-O, Ag(111)+$( 7\!\times\!\surd3 ) \mathrm{rect}$-$\mathrm{SO}_4$, Ru(0001)+$( \surd3\!\times\!\surd3 ) \mathrm{R30^\circ}$-C. TMB stands for 1,3,5-tris(4-mercaptophenyl)-benzene with chemical formula C$_{24}$H$_{15}$S$_3$. We are able to report substantially improved reliability factors.

cond-mat.mtrl-sci↗

arXiv2013

The Structure and Local Variations of the Graphene Moiré on Ir(111)

We have studied the incommensurate moiré structure of epitaxial graphene grown on iridium(111) by dynamic low energy electron diffraction [LEED-I(V)] and non-contact atomic force microscopy (AFM) with a CO terminated tip. Our LEED-I(V) results yield the average positions of all the atoms in the surface unit cell and are in qualitative agreement with the structure obtained from density functional theory (DFT). The AFM experiments reveal local variations of the moiré structure: the corrugation varies smoothly over several moiré unit cells between 42 and 56 pm. We attribute these variations to the varying registry between the moiré symmetry sites and the underlying substrate. We also observe isolated outliers, where the moiré top sites can be offset by an additional 10 pm. This study demonstrates that AFM imaging can be used to directly yield the local surface topography with pm accuracy even on incommensurate 2D structures with varying chemical reactivity.

cond-mat.mtrl-sci↗

arXiv2013

Adsorption structure determination of a large polyaromatic trithiolate on Cu(111): combination of LEED-I(V) and DFT-vdW

The adsorption geometry of 1,3,5-tris(4-mercaptophenyl)benzene (TMB) on Cu(111) is determined with high precision using two independent methods, experimentally by quantitative low energy electron diffraction (LEED-I(V)) and theoretically by dispersion corrected density functional theory (DFT-vdW). Structural refinement using both methods consistently results in similar adsorption sites and geometries. Thereby a level of confidence is reached that allows deduction of subtle structural details such as molecular deformations or relaxations of copper substrate atoms.

cond-mat.mtrl-sci↗

arXiv2009

Partial dissociation of water on Fe$_{3}$O$_{4}$(001): adsorbate induced charge and orbital order

The interaction of water with Fe$_3$O$_4$(001) is studied by density functional theory (DFT) calculations including an on-site Coulomb term. For isolated molecules dissociative adsorption is strongly promoted at surface defect sites, while at higher coverages a hydrogen-bonded network forms with alternating molecular and dissociated species. This mixed adsorption mode and a suppression of the $(\sqrt{2}\times \sqrt{2})R45^{\circ}$-reconstruction are confirmed by a quantitative low energy electron diffraction (LEED) analysis. Adsorbate induced electron transfer processes add a new dimension towards understanding the catalytic activity of magnetite(001).

cond-mat.mtrl-sci↗