The RuO2 (100) surface exposes regions with (1× 1) and c (2× 2) symmetry. The (1× 1) phase is ver... more The RuO2 (100) surface exposes regions with (1× 1) and c (2× 2) symmetry. The (1× 1) phase is very active in oxidizing CO, while the c (2× 2) phase is inactive because CO does not adsorb on the c (2× 2) phase above 100 K. This experimental finding suggests the ...
Chemphyschem : a European journal of chemical physics and physical chemistry, Jan 20, 2004
The visualization of surface reactions on the atomic scale provides direct insight into the micro... more The visualization of surface reactions on the atomic scale provides direct insight into the microscopic reaction steps taking place in a catalytic reaction at a (model) catalyst's surface. Employing the technique of scanning tunneling microscopy (STM), we investigated the CO oxidation reaction over the RuO2(110) and RuO2(100) surfaces. For both surfaces the protruding bridging O atoms are imaged in STM as bright features. The reaction mechanism is identical on both orientations of RuO2. CO molecules adsorb on the undercoordinated surface Ru atoms from where they recombine with undercoordinated O atoms to form CO2 at the oxide surface. In contrast to the RuO2(110) surface, the RuO2(100) surface stabilizes also a catalytically inactive c(2 x 2) surface phase onto which CO is not able to adsorb above 100 K. We argue that this inactive RuO2(100)-c(2 x 2) phase may play an important role in the deactivation of RuO2 catalysts in the electrochemical Cl2 evolution and other heterogeneou...
Unlike phonons in crystals, the collective excitations in liquids cannot be treated as propagatio... more Unlike phonons in crystals, the collective excitations in liquids cannot be treated as propagation of harmonic displacements of atoms around stable local energy minima. The viscoelasticity of liquids, reflected in transition from the adiabatic to elastic high-frequency speed of sound and in absence of the long-wavelength transverse excitations, results in dispersions of longitudinal (L) and transverse (T) collective excitations essentially different from the typical phonon ones. Practically, nothing is known about the effect of high pressure on the dispersion of collective excitations in liquids, which causes strong changes in liquid structure. Here dispersions of L and T collective excitations in liquid Li in the range of pressures up to 186 GPa were studied by ab initio simulations. Two methodologies for dispersion calculations were used: direct estimation from the peak positions of the L/T current spectral functions and simulation-based calculations of wavenumber-dependent collective eigenmodes. It is found that at ambient pressure, the longitudinal and transverse dynamics are well separated, while at high pressures, the transverse current spectral functions, density of vibrational states, and dispersions of collective excitations yield evidence of two types of propagating modes that contribute strongly to transverse dynamics. Emergence of the unusually high-frequency transverse modes gives evidence of the breakdown of a regular viscoelastic theory of transverse dynamics, which is based on coupling of a single transverse propagating mode with shear relaxation. The explanation of the observed high-frequency shift above the viscoelastic value is given by the presence of another branch of collective excitations. With the pressure increasing, coupling between the two types of collective excitations is rationalized within a proposed extended viscoelastic model of transverse dynamics.
High Performance Computing in Science and Engineering `07, 2008
... of Emim-chloroaluminate Ionic Liquids Barbara Kirchner1 and Ari P. Seitsonen2 ... Therefore t... more ... of Emim-chloroaluminate Ionic Liquids Barbara Kirchner1 and Ari P. Seitsonen2 ... Therefore the application of GGA-density functional theory is necessary in order to make the simulation computationally tractable. ... 17. Z. Meng, A. Dölle, and WR Carper. J. Mol. ...
AA (Physikalisch-Chemisches Institut, Justus-Liebig-Universität, Heinrich-Buff-Ring 58, D-35392 G... more AA (Physikalisch-Chemisches Institut, Justus-Liebig-Universität, Heinrich-Buff-Ring 58, D-35392 Gießen, Germany), AB (Lehrstuhl für Technische Chemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany), AC (IMPMC, CNRS and Université Pierre et Marie Curie, 4 ...
We briefly summarize our joint effort to understand catalytic reactions on the model catalyst RuO... more We briefly summarize our joint effort to understand catalytic reactions on the model catalyst RuO2 (110) on the atomic scale, applying state-of-the-art density functional theory calculations and surface chemical characterizations in parallel. This intimate theory/ ...
The structure of the (3 3 1) reconstructions of the Si (111) and Ge (111) surfaces induced by ads... more The structure of the (3 3 1) reconstructions of the Si (111) and Ge (111) surfaces induced by adsorption of alkali metals has been determined on the basis of surface x-ray diffraction and low-energy electron diffraction measurements and density functional theory. The (3 3 1) ...
... Surface and interface chemistry. Chemisorption. Body. I. INTRODUCTION. In the past, numerous ... more ... Surface and interface chemistry. Chemisorption. Body. I. INTRODUCTION. In the past, numerous studies were devoted to the interaction of hydrogen with metal single-crystal surfaces, whereby, less frequently, adsorption geometries were also determined (for reviews, see Refs. ) ...
The RuO2 (100) surface exposes regions with (1× 1) and c (2× 2) symmetry. The (1× 1) phase is ver... more The RuO2 (100) surface exposes regions with (1× 1) and c (2× 2) symmetry. The (1× 1) phase is very active in oxidizing CO, while the c (2× 2) phase is inactive because CO does not adsorb on the c (2× 2) phase above 100 K. This experimental finding suggests the ...
Chemphyschem : a European journal of chemical physics and physical chemistry, Jan 20, 2004
The visualization of surface reactions on the atomic scale provides direct insight into the micro... more The visualization of surface reactions on the atomic scale provides direct insight into the microscopic reaction steps taking place in a catalytic reaction at a (model) catalyst's surface. Employing the technique of scanning tunneling microscopy (STM), we investigated the CO oxidation reaction over the RuO2(110) and RuO2(100) surfaces. For both surfaces the protruding bridging O atoms are imaged in STM as bright features. The reaction mechanism is identical on both orientations of RuO2. CO molecules adsorb on the undercoordinated surface Ru atoms from where they recombine with undercoordinated O atoms to form CO2 at the oxide surface. In contrast to the RuO2(110) surface, the RuO2(100) surface stabilizes also a catalytically inactive c(2 x 2) surface phase onto which CO is not able to adsorb above 100 K. We argue that this inactive RuO2(100)-c(2 x 2) phase may play an important role in the deactivation of RuO2 catalysts in the electrochemical Cl2 evolution and other heterogeneou...
Unlike phonons in crystals, the collective excitations in liquids cannot be treated as propagatio... more Unlike phonons in crystals, the collective excitations in liquids cannot be treated as propagation of harmonic displacements of atoms around stable local energy minima. The viscoelasticity of liquids, reflected in transition from the adiabatic to elastic high-frequency speed of sound and in absence of the long-wavelength transverse excitations, results in dispersions of longitudinal (L) and transverse (T) collective excitations essentially different from the typical phonon ones. Practically, nothing is known about the effect of high pressure on the dispersion of collective excitations in liquids, which causes strong changes in liquid structure. Here dispersions of L and T collective excitations in liquid Li in the range of pressures up to 186 GPa were studied by ab initio simulations. Two methodologies for dispersion calculations were used: direct estimation from the peak positions of the L/T current spectral functions and simulation-based calculations of wavenumber-dependent collective eigenmodes. It is found that at ambient pressure, the longitudinal and transverse dynamics are well separated, while at high pressures, the transverse current spectral functions, density of vibrational states, and dispersions of collective excitations yield evidence of two types of propagating modes that contribute strongly to transverse dynamics. Emergence of the unusually high-frequency transverse modes gives evidence of the breakdown of a regular viscoelastic theory of transverse dynamics, which is based on coupling of a single transverse propagating mode with shear relaxation. The explanation of the observed high-frequency shift above the viscoelastic value is given by the presence of another branch of collective excitations. With the pressure increasing, coupling between the two types of collective excitations is rationalized within a proposed extended viscoelastic model of transverse dynamics.
High Performance Computing in Science and Engineering `07, 2008
... of Emim-chloroaluminate Ionic Liquids Barbara Kirchner1 and Ari P. Seitsonen2 ... Therefore t... more ... of Emim-chloroaluminate Ionic Liquids Barbara Kirchner1 and Ari P. Seitsonen2 ... Therefore the application of GGA-density functional theory is necessary in order to make the simulation computationally tractable. ... 17. Z. Meng, A. Dölle, and WR Carper. J. Mol. ...
AA (Physikalisch-Chemisches Institut, Justus-Liebig-Universität, Heinrich-Buff-Ring 58, D-35392 G... more AA (Physikalisch-Chemisches Institut, Justus-Liebig-Universität, Heinrich-Buff-Ring 58, D-35392 Gießen, Germany), AB (Lehrstuhl für Technische Chemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany), AC (IMPMC, CNRS and Université Pierre et Marie Curie, 4 ...
We briefly summarize our joint effort to understand catalytic reactions on the model catalyst RuO... more We briefly summarize our joint effort to understand catalytic reactions on the model catalyst RuO2 (110) on the atomic scale, applying state-of-the-art density functional theory calculations and surface chemical characterizations in parallel. This intimate theory/ ...
The structure of the (3 3 1) reconstructions of the Si (111) and Ge (111) surfaces induced by ads... more The structure of the (3 3 1) reconstructions of the Si (111) and Ge (111) surfaces induced by adsorption of alkali metals has been determined on the basis of surface x-ray diffraction and low-energy electron diffraction measurements and density functional theory. The (3 3 1) ...
... Surface and interface chemistry. Chemisorption. Body. I. INTRODUCTION. In the past, numerous ... more ... Surface and interface chemistry. Chemisorption. Body. I. INTRODUCTION. In the past, numerous studies were devoted to the interaction of hydrogen with metal single-crystal surfaces, whereby, less frequently, adsorption geometries were also determined (for reviews, see Refs. ) ...
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