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2. Diffusion- and reaction-limited cluster aggregation revisited

Author

Jungblut, Swetlana, Joswig, Jan-Ole, and Eychmüller, Alexander

Subjects
Condensed Matter - Soft Condensed Matter, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We simulated irreversible aggregation of non-interacting particles and of particles interacting via repulsive and attractive potentials explicitly implementing the rotational diffusion of aggregating clusters. Our study confirms that the attraction between particles influences neither the aggregation mechanism nor the structure of the aggregates, which are identical to those of non-interacting particles. In contrast, repulsive particles form more compact aggregates and their fractal dimension and aggregation times increase with the decrease of the temperature. A comparison of the fractal dimensions obtained for non-rotating clusters of non-interacting particles and for rotating clusters of repulsive particles provides an explanation for the conformity of the respective values obtained earlier in the well established model of diffusion-limited cluster aggregation neglecting rotational diffusion and in experiments on colloidal particles., Comment: 7 pages, 6 figures, and supplementary material

Published
2019
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3. Diffusion-limited cluster aggregation: Impact of rotational diffusion

Author

Jungblut, Swetlana, Joswig, Jan-Ole, and Eychmüller, Alexander

Subjects
Condensed Matter - Soft Condensed Matter, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Diffusion-limited cluster aggregation (DLCA) is a well established model for the formation of highly porous low-density non-equilibrium structures. One of the main conclusions of the previous studies considering this model is that the rotational diffusion of aggregating clusters does not change their structure characterized by a universal fractal dimension of $d_f=1.7-1.8$. In contradiction to this assumption, we demonstrate that the rotation movement of clusters significantly changes the structure of forming aggregates. The fractal dimension of rotating clusters is lower than the one found in the standard DLCA model and decreases with the increasing ratio of rotational and translational diffusion constants $D_r/D_t$, which offers a possibility to tune the structures of the aggregates below the conventional DLCA fractal dimension limit., Comment: 5 pages, 4 figures

Published
2018
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8. Understanding MOF Flexibility: An Analysis Focused on Pillared Layer MOFs as a Model System

Author

Senkovska, Irena, primary, Bon, Volodymyr, additional, Abylgazina, Leila, additional, Mendt, Matthias, additional, Berger, Jan, additional, Kieslich, Gregor, additional, Petkov, Petko, additional, Fiorio, Jhonatan Luiz, additional, Joswig, Jan-Ole, additional, Heine, Thomas, additional, Schaper, Larissa, additional, Bachetzky, Christopher, additional, Schmid, Rochus, additional, Fischer, Roland A., additional, Pöppl, Andreas, additional, Brunner, Eike, additional, and Kaskel, Stefan, additional

Published
2023
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11. Isotope-selective pore opening in a flexible metal-organic framework

Author

Bondorf, Linda, primary, Fiorio, Jhonatan Luiz, additional, Bon, Volodymyr, additional, Zhang, Linda, additional, Maliuta, Mariia, additional, Ehrling, Sebastian, additional, Senkovska, Irena, additional, Evans, Jack D., additional, Joswig, Jan-Ole, additional, Kaskel, Stefan, additional, Heine, Thomas, additional, and Hirscher, Michael, additional

Published
2022
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19. Optical properties of cadmium sulfide clusters

Author

Joswig, Jan-Ole, Seifert, Gotthard, Niehaus, Thomas A., and Springborg, Michael

Subjects
Stoichiometry -- Research, Sulfides -- Optical properties, Chemicals, plastics and rubber industries
Abstract

The excitation spectra of stoichiometric cadmium sulfide clusters are calculated upto 144 atoms using a time-dependent extension of a density-functional tight-binding method. The spectra show a strong dependency of the lowest unoccupied molecular orbitals on the structural properties of the clusters, especially on the number of single-bonded surface bonds.

Published
2003

24. Structural and electronic properties of cadmium sulfide clusters

Author

Joswig, Jan-Ole, Springborg, Michael, and Seifert, Gotthard

Subjects
Cadmium -- Research, Sulfides -- Research, Chemicals, plastics and rubber industries
Abstract

Stoichiometric CdnSn clusters are shown to rely on n for n up to around 100.

Published
2000

25. Specific-Ion Effects Directed Noble Metal Aerogels: Versatile Manipulation for Electrocatalysis and Beyond

Author

Du, Ran, Hu, Yue, Hübner, René, Joswig, Jan-Ole, Fan, Xuelin, Schneider, Kristian, and Eychmüller, Alexander

Subjects
Chemistry, Materials Science, SciAdv r-articles, Research Articles, Research Article
Abstract

Specific ion effects are demonstrated to create and flexibly manipulate noble metal aerogels for versatile applications., Noble metal foams (NMFs) are a new class of functional materials featuring properties of both noble metals and monolithic porous materials, providing impressive prospects in diverse fields. Among reported synthetic methods, the sol-gel approach manifests overwhelming advantages for versatile synthesis of nanostructured NMFs (i.e., noble metal aerogels) under mild conditions. However, limited gelation methods and elusive formation mechanisms retard structure/composition manipulation, hampering on-demand design for practical applications. Here, highly tunable NMFs are fabricated by activating specific ion effects, enabling various single/alloy aerogels with adjustable composition (Au, Ag, Pd, and Pt), ligament sizes (3.1 to 142.0 nm), and special morphologies. Their superior performance in programmable self-propulsion devices and electrocatalytic alcohol oxidation is also demonstrated. This study provides a conceptually new approach to fabricate and manipulate NMFs and an overall framework for understanding the gelation mechanism, paving the way for on-target design of NMFs and investigating structure-performance relationships for versatile applications.

Published
2019
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32. The influence of C2 dimers on the stability of TimCn metcar clusters.

Author

Joswig, Jan-Ole and Springborg, Michael

Subjects
*CARBON compounds, *DIMERS, *TRANSITION metals, *STOICHIOMETRY, *CUBIC curves, *TITANIUM, *METAL clusters
Abstract

We present results of an investigation of small TimCn clusters with different stoichiometries in order to throw light on the occurrence of carbon dimers in these structures. Previous studies of transition metal (M) metallocarbohedrene (metcar) clusters MmCn have proposed that C2 dimers play a special role. In the special case of TimCn metcars these dimers have been observed in several studies. We shall show that clusters containing C2 dimers are energetically favored with respect to those containing only single carbon atoms or trimers, especially when the dimers occupy the corner positions of cubic clusters. Moreover, we find that cubic structures are more stable than corresponding double-cage metcars. Finally, a highly symmetric Ti6C10 metcar cluster is presented and proposed to be the global-minimum structure of this stoichiometry. [ABSTRACT FROM AUTHOR]

Published
2008
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33. Photoabsorption in sodium clusters on the basis of time-dependent density-functional theory.

Author

Joswig, Jan-Ole, Tunturivuori, Lasse O., and Nieminen, Risto M.

Subjects
*EXCITON theory, *ABSORPTION, *CLUSTER theory (Nuclear physics), *NUCLEAR isomers, *ELECTRONS
Abstract

The photoabsorption spectra of a continuous series of Nan clusters (n<=14, n=20, n=40) have been calculated using a time-dependent density-functional scheme. Accordingly, we present these spectra and show that they are in very good agreement with other theoretically and experimentally obtained photoabsorption spectra. Furthermore, we discuss the influence of the cluster structure on the photoabsorption spectrum for some selected clusters and present for several cluster sizes photoabsorption spectra of different geometrical isomers. The spectra of clusters with five or more atoms are dominated by a few large peaks which can be interpreted as collective plasmon excitations [ABSTRACT FROM AUTHOR]

Published
2008
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34. Tubular structures from the LnS–TaS₂ (Ln = La, Ce, Nd, Ho, Er) and LaSe–TaSe₂ misfit layered compounds

Author

Radovsky, Gal, Popovitz-Biro, Ronit, Lorenz, Tommy, Joswig, Jan-Ole, Seifert, Gotthard, Houben, Lothar, Dunin-Borkowski, Rafal E., and Tenne, Reshef

Subjects
Nanotube-shaped structures, stress relaxation, Raman spectroscopy, theoretical calculation, ddc:621.3, ddc:540, ddc:530, ddc:620, Nanoröhrenförmige Strukturen, Spannungsrelaxation, Ramanspektroskopie, theoretische Berechnung
Abstract

Nanotubular structures from a new family of misfit compounds LnS–TaS₂ with (Ln = La, Ce, Nd, Ho, Er) and LaSe–TaSe₂ (some of them not known hitherto) are reported. Stress relaxation originating from the lattice mismatch between the alternating LnS(Se) and TaS₂(Se) layers, combined with seaming of the dangling bonds in the rim, leads to the formation of a variety of nanotubular structures. Their structures are studied via scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM) and selected area electron diffraction (SAED). Tubules exhibiting a single folding vector for the LnS(Se) as well as TaS₂(Se) layers were often found. The small values of the c-axis periodicities are indicative of a strong interaction between the two constituent layers which was also supported by Raman spectroscopy and theoretical calculations.

Published
2016

38. Tetrahedral amorphous carbon coatings for friction reduction of the valve train in internal combustion engines

Author

Götze, Andreas, Makowski, Stefan, Kunze, Tim, Hübner, Matthias, Zellbeck, Hans, Weihnacht, Volker, Leson, Andreas, Beyer, Eckhard, Joswig, Jan-Ole, Seifert, Gotthard, Abrasonis, Gintautas, Posselt, Matthias, Fassbender, Jürgen, Möller, Wolfhard, Gemming, Sibylle, Krause, Matthias, and Publica

Abstract

Tetrahedral amorphous carbon (ta-C) is studied as a tribological coating for the valve train's exhaust camshaft of a combustion engine. The coated camshafts were installed in a non-fired engine, tested in a computerized component test bench under practice-relevant conditions and analyzed for their frictional behavior. A notable reduction of the valve train's drive torque on the test bench is demonstrated. Namely, on a roller cam system with ta-C-coated camshaft the reduction is about 15% in average within the entire engine-map. The ta-C coatings were extensively characterized under laboratory conditions before and after the investigations on the test bench. Mechanistic understanding of the tribological behavior of ta-C coatings under dry or starving lubricated conditions was achieved by atomistic simulations of the tribological contact. Industrial utilization of these results would lead to a significant increase of the energy efficiency of combustion engines.

Published
2014

40. Preface

Author

Springborg, Michael, primary and Joswig, Jan-Ole, additional

Published
2016
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43. Charge Transfer Variability in Misfit Layer Compounds: Comparison of SnS-SnS2 and LaS-TaS2.

Author

Lorenz, Tommy, Baburin, Igor A., Joswig, Jan‐Ole, and Seifert, Gotthard

Subjects
CHARGE transfer, CHEMICALS, DENSITY functional theory, QUASIMOLECULES, CHEMICAL bonds
Abstract

The present paper compares and discusses two selected misfit (layer) compounds exemplarily, namely SnS-SnS2 and LaS-TaS2. We have employed a density-functional theory-based approach to calculate structural, energetic, and electronic properties of these structures. We have put emphasis on the difference between single layers, combined double-layer systems and periodically stacked bulk structures. Especially the varying magnitudes of charge transfer between the sublayers were studied. We demonstrate how the chemical constitution of the sublayers affects the interlayer interactions: these may be a weak non-bonding van-der-Waals dominated interlayer interaction as in SnS-SnS2 and many other layered structures or a strong interaction related to a remarkable charge transfer between the layers as in LaS-TaS2. [ABSTRACT FROM AUTHOR]

Published
2017
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44. Preface

Author

Springborg, Michael, primary and Joswig, Jan-Ole, additional

Published
2015
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