Publikationsliste Jun.-Prof. Dr. Christian Dreßler

Anzahl der Treffer: 21
Erstellt: Wed, 24 Apr 2024 23:16:43 +0200 in 0.1036 sec

Hannappel, Thomas; Shekarabi, Sahar; Jaegermann, Wolfram; Runge, Erich; Hofmann, Jan Philipp; Krol, Roel van de; May, Matthias M.; Paszuk, Agnieszka; Hess, Franziska; Bergmann, Arno; Bund, Andreas; Cierpka, Christian; Dreßler, Christian; Dionigi, Fabio; Friedrich, Dennis; Favaro, Marco; Krischok, Stefan; Kurniawan, Mario; Lüdge, Kathy; Lei, Yong; Roldán Cuenya, Beatriz; Schaaf, Peter; Schmidt-Grund, Rüdiger; Schmidt, W. Gero; Strasser, Peter; Unger, Eva; Montoya, Manuel Vasquez; Wang, Dong; Zhang, Hongbin
Integration of multi-junction absorbers and catalysts for efficient solar-driven artificial leaf structures : a physical and materials science perspective. - In: Solar RRL, ISSN 2367-198X, Bd. 0 (2024), 0, S. 1-88

Artificial leaves could be the breakthrough technology to overcome the limitations of storage and mobility through the synthesis of chemical fuels from sunlight, which will be an essential component of a sustainable future energy system. However, the realization of efficient solar-driven artificial leaf structures requires integrated specialized materials such as semiconductor absorbers, catalysts, interfacial passivation, and contact layers. To date, no competitive system has emerged due to a lack of scientific understanding, knowledge-based design rules, and scalable engineering strategies. Here, we will discuss competitive artificial leaf devices for water splitting, focusing on multi-absorber structures to achieve solar-to-hydrogen conversion efficiencies exceeding 15%. A key challenge is integrating photovoltaic and electrochemical functionalities in a single device. Additionally, optimal electrocatalysts for intermittent operation at photocurrent densities of 10-20 mA cm^-2 must be immobilized on the absorbers with specifically designed interfacial passivation and contact layers, so-called buried junctions. This minimizes voltage and current losses and prevents corrosive side reactions. Key challenges include understanding elementary steps, identifying suitable materials, and developing synthesis and processing techniques for all integrated components. This is crucial for efficient, robust, and scalable devices. Here, we discuss and report on corresponding research efforts to produce green hydrogen with unassisted solar-driven (photo-)electrochemical devices. This article is protected by copyright. All rights reserved.
Kunze, Thomas; Dreßler, Christian; Lauer, Christian; Paul, Wolfgang; Sebastiani, Daniel
Reverse mapping of coarse grained polyglutamine conformations from PRIME20 sampling. - In: ChemPhysChem, ISSN 1439-7641, (2024), e202300521, S. 1-11

An inverse coarse-graining protocol is presented for generating and validating atomistic structures of large (bio-) molecules from conformations obtained via a coarse-grained sampling method. Specifically, the protocol is implemented and tested based on the (coarse-grained) PRIME20 protein model (P20/SAMC), and the resulting all-atom conformations are simulated using conventional biomolecular force fields. The phase space sampling at the coarse-grained level is performed with a stochastical approximation Monte Carlo approach. The method is applied to a series of polypeptides, specifically dimers of polyglutamine with varying chain length in aqueous solution. The majority (>70 %) of the conformations obtained from the coarse-grained peptide model can successfully be mapped back to atomistic structures that remain conformationally stable during 10 ns of molecular dynamics simulations. This work can be seen as the first step towards the overarching goal of improving our understanding of protein aggregation phenomena through simulation methods.
Dreßler, Christian; Hänseroth, Jonas; Sebastiani, Daniel
Coexistence of cationic and anionic phosphate moieties in solids: unusual but not impossible. - In: The journal of physical chemistry letters, ISSN 1948-7185, Bd. 14 (2023), 32, S. 7249-7255

Phosphoric acid is commonly known either as a neutral molecule or as an anion (phosphate). We theoretically confirm by ab initio molecular dynamics simulations (AIMD) that a cationic form H4PO4+ coexists with the anionic form H2PO4- in the same salt. This paradoxical situation is achieved by partial substitution of Cs+ by H4PO4+ in CsH2PO4. Thus, HnPO4 acts simultaneously as both the positive and the negative ion of the salt. We analyze the dynamical protonation pattern within the unusual hydrogen bond network that is established between the ions. Our AIMD simulations show that a conventional assignment of protonation states of the phosphate groups is not meaningful. Instead, a better description of the protonation situation is achieved by an efficiently fractional assignment of the strongly hydrogen-bonded protons to both its nearest and next-nearest oxygen neighbors.
Flecken, Franziska; Knapp, Anna; Grell, Toni; Dreßler, Christian; Hanf, Schirin
Acute bite angle POP- and PSP-type ligands and their trinuclear copper(I) complexes: synthesis and photo-luminescence properties. - In: Inorganic chemistry, ISSN 1520-510X, Bd. 62 (2023), 32, S. 13038-13049

In the current work, the rational synthesis of trinuclear copper complexes, incorporating acute bite angle POP- and PSP-type ligands, is reported. The in situ formation of POP (Ph2P–O–PPh2) or PSP (Ph2P–S–PPh2) ligands in the presence of a copper(I) precursor gave access to various trinuclear copper complexes of the form [Cu3(μ3-Hal)2(μ-PXP)3]PF6 [X = O; Hal = Cl (1), Br (2), I (3) and X = S; Hal = Cl (5), Br (6), I (7)]. Related iodide-containing complexes and clusters, such as [Cu4(μ3-I)4(Ph2PI)4] (4) and [Cu3(μ3-I)2(μ-I)(μ-PSP)2] (8), could also be obtained via the variation of the reaction stoichiometry. The investigation of the photo-optical properties by photo-luminescence spectroscopy has demonstrated that the phosphorescence in the visible region can be switched off through the mere change of the heteroatom in the ligand backbone (POP vs PSP ligand scaffold). Theoretical studies have been conducted to complement the experimental photo-optical data with detailed insights into the occurring electronic transitions. Consequently, this systematic study paves the way for tuning the photo-optical properties of transition metal complexes in a more rational way.
Kunze, Thomas; Dreßler, Christian; Sebastiani, Daniel
Secondary structure formation in hybrid synthetic/peptide polymers: insights from molecular dynamics simulations. - In: Macromolecular theory and simulations, ISSN 1521-3919, Bd. 32 (2023), 3, 2200070, S. 1-8

Proteins and peptides exhibit an immense variety of structures, which are generally classified according to simple structural motifs (mainly α helices and β sheets). Considerable efforts have been invested in understanding the relationship between chemical structure (primary structure) of peptides and their spatial motifs (secondary structure). However, little is known about the possibility to interfere intentionally in these structural driving forces, for example, by inserting (short) artificial polymer chains in the peptide backbone. Structure formation on such hybrid synthetic/biochemical polymers is still an emerging field of research. Here, molecular dynamics simulations are used to illustrate the influence of inserted polyethylene segments on the secondary structure of several peptide homopolymers. A loss of structure of ≈50% when the peptide chain length drops to ten amino acids and a practically complete absence for even shorter peptide segments.
Kirsch, Christoph; Dreßler, Christian; Sebastiani, Daniel
Atomistic diffusion pathways of lithium ions in crystalline lithium silicides from ab initio molecular dynamics simulations. - In: The journal of physical chemistry, ISSN 1932-7455, Bd. 126 (2022), 29, S. 12136-12149

The LixSiy class of compounds exhibits a broad variety of crystal structures with high experimentally observed lithium diffusivities. We explore lithium diffusion in a series of LixSiy by means of ab initio molecular dynamics simulations and find a strong variability of diffusion coefficients in the defect-free crystal structures. We explain the microscopic origin of these variations in order to characterize the mobility of lithium ions, both from a local and from a long-range perspective. Our study reveals the existence of important interstitial sites. We identify different types of diffusion pathways in our simulation trajectories and report their energy profiles. It turns out that the diffusive behavior of lithium in these compounds is governed by only a few diffusion paths. We show the connection between diffusion mechanisms and energy barriers and especially highlight the relevance of point defects. We observe considerable structural relaxation within a radius of about 3.5 Å around the diffusion path.
Dreßler, Christian; Sebastiani, Daniel
Polarization energies from efficient representation of the linear density-density response function. - In: Advanced theory and simulations, ISSN 2513-0390, Bd. 4 (2021), 4, 2000260, S. 1-10

The authors present a proof-of-concept study for the calculation of atomic forces on a solvated molecule by means of the linear density-density response function in its moment expanded representation. The density-density response function represents an efficient way to compute molecular forces for arbitrary external potentials via an ab initio scheme, without the need to perform an explicit self-consistent quantum chemical calculation for each configuration of the chemical environment. Here, the authors show that it is indeed possible to determine the atomic forces of interacting bulk-like molecular complexes due to polarization effects of the surrounding molecules with good accuracy. This study represents a significant step the practical applicability of the approach, which is still in a development phase. The potential application of the computational scheme in terms of molecular dynamics simulations is illustrated by considering a variety of cluster conformations, as they would be found within a molecular dynamics trajectory.
Dreßler, Christian; Kabbe, Gabriel; Brehm, Martin; Sebastiani, Daniel
Dynamical matrix propagator scheme for large-scale proton dynamics simulations. - In: The journal of chemical physics, ISSN 1089-7690, Bd. 152 (2020), 11, 114114, insges. 14 S.

We derive a matrix formalism for the simulation of long range proton dynamics for extended systems and timescales. On the basis of an ab initio molecular dynamics simulation, we construct a Markov chain, which allows us to store the entire proton dynamics in an M × M transition matrix (where M is the number of oxygen atoms). In this article, we start from common topology features of the hydrogen bond network of good proton conductors and utilize them as constituent constraints of our dynamic model. We present a thorough mathematical derivation of our approach and verify its uniqueness and correct asymptotic behavior. We propagate the proton distribution by means of transition matrices, which contain kinetic data from both ultra-short (sub-ps) and intermediate (ps) timescales. This concept allows us to keep the most relevant features from the microscopic level while effectively reaching larger time and length scales. We demonstrate the applicability of the transition matrices for the description of proton conduction trends in proton exchange membrane materials.
Dreßler, Christian; Kabbe, Gabriel; Brehm, Martin; Sebastiani, Daniel
Exploring non-equilibrium molecular dynamics of mobile protons in the solid acid CsH2PO4 at the micrometer and microsecond scale. - In: The journal of chemical physics, ISSN 1089-7690, Bd. 152 (2020), 16, 164110, insges. 13 S.

We explicitly compute the non-equilibrium molecular dynamics of protons in the solid acid CsH2PO4 on the micrometer length scale via a multiscale Markov model: The molecular dynamics/matrix propagation (MDM) method. Within the MDM approach, the proton dynamics information of an entire molecular dynamics simulation can be condensed into a single M × M matrix (M is the number of oxygen atoms in the simulated system). Due to this drastic reduction in the complexity, we demonstrate how to increase the length and time scales in order to enable the simulation of inhomogeneities of CsH2PO4 systems at the nanometer scale. We incorporate explicit correlation of protonation dynamics with the protonation state of the neighboring proton sites and illustrate that this modification conserves the Markov character of the MDM method. We show that atomistic features such as the mean square displacement and the diffusion coefficient of the protons can be computed quantitatively from the matrix representation. Furthermore, we demonstrate the application potential of the scheme by computing the explicit dynamics of a non-equilibrium process in an 8 μm CsH2PO4 system during 5 ms.
Dreßler, Christian; Sebastiani, Daniel
Effect of anion reorientation on proton mobility in the solid acids family CsHyXO4 (X = S, P, Se, y = 1, 2) from ab initio molecular dynamics simulations. - In: Physical chemistry, chemical physics, ISSN 1463-9084, Bd. 22 (2020), 19, S. 10738-10752
Im Titel sind y und 4 in CsHyXO4 tiefgestellt

The high temperature phases of the solid acids CsHSeO4, CsHSO4 and CsH2PO4 show extraordinary high proton conductivities, while the low temperature phases do not conduct protons at all. We systematically investigate proton dynamics in the low and high temperature phases of these compounds by means of ab initio molecular dynamics simulations in order to develop a general picture of the proton transfer mechanism. For all of these compounds, proton conduction follows a Grotthuss mechanism via a combined proton transfer and subsequent structural reorientation of the environment. We demonstrate that the drastically reduced conductivity of the low temperature phases is caused by a highly ordered, rigid hydrogen bond network, while efficient long range proton transfer in the high temperature phases is enabled by the interplay of high proton transfer rates and frequent anion reorientation. Furthermore, we present a simple descriptor for the quantitative prediction of the diffusion coefficient within the solid acids family. As a side result, we show that the rate of the most elementary proton hopping reaction depends on the heavy-atom configuration of the nearest atoms in a ubiquitous manner, and is in turn almost independent from the global nature of the compound, i.e. whether it is organic or inorganic, ordered or disordered.