TY - GEN A1 - Lemke, Mathias A1 - Stein, Lewin A1 - Hölter, Arne A1 - Weinzierl, Stefan T1 - Adjungierten-basierte Synthese und Bestimmung optimaler Treiberfunktionen von Lautsprechern mit komplexer Richtcharakteristik N2 - Die Bestimmung optimaler Treiberfunktionen von Lautsprechern mit frequenzabhängiger Richtcharakteristik ist ein schlecht gestelltes Optimierungsproblem. Zu dessen Lösung haben die Autoren in vorangegangenen Beiträgen eine adjungierten-basierte Methode zur Optimierung von Lautsprecher-Arrays im Zeitbereich vorgestellt [5, 6, 8]. Diese ermöglicht unter anderem die Berücksichtigung von Berandungen und Umgebungseffekten wie Wind, war jedoch bisher auf monopol-artige Quellen beschränkt. Um diese Einschränkung zu beheben, haben die Autoren einen adjungierten-basierten Zeitbereichsansatz mit Finiten-Differenzen (FDTD) zur Synthese komplexer synthetischer Schallquellen durch diskrete, gitter-basierte Monopole vorgestellt [4, 9]. In diesem Beitrag demonstrieren die Autoren die entsprechende Modellierung eines realen Zweiwege-Monitors (A). Zudem wird gezeigt, wie sich die Vielzahl der zur Synthese verwendeten Monopole in eine Lautsprecher-Treiberfunktion überführen lassen (B). Y1 - 2021 SN - 978-3-939296-18-8 U6 - https://doi.org/https://doi.org/10.14279/depositonce-12515 PB - Deutsche Gesellschaft für Akustik e.V. ER - TY - JOUR A1 - Leser, Ulf A1 - Hilbrich, Marcus A1 - Draxl, Claudia A1 - Eisert, Peter A1 - Grunske, Lars A1 - Hostert, Patrick A1 - Kainmüller, Dagmar A1 - Kao, Odej A1 - Kehr, Birte A1 - Kehrer, Timo A1 - Koch, Christoph A1 - Markl, Volker A1 - Meyerhenke, Henning A1 - Rabl, Tilmann A1 - Reinefeld, Alexander A1 - Reinert, Knut A1 - Ritter, Kerstin A1 - Scheuermann, Björn A1 - Schintke, Florian A1 - Schweikardt, Nicole A1 - Weidlich, Matthias T1 - The Collaborative Research Center FONDA JF - Datenbank-Spektrum Y1 - 2021 U6 - https://doi.org/10.1007/s13222-021-00397-5 VL - 21 IS - 3 SP - 255 EP - 260 ER - TY - JOUR A1 - Pathania, Yogyata A1 - Chakraborty, Dipanjan A1 - Höfling, Felix T1 - Continuous demixing transition of binary liquids: finite-size scaling from the analysis of sub-systems JF - Advances Theory and Simulation Y1 - 2021 U6 - https://doi.org/10.1002/adts.202000235 VL - 4 SP - 2000235 ER - TY - JOUR A1 - Frömberg, Daniela A1 - Höfling, Felix T1 - Generalized master equation for first-passage problems in partitioned spaces JF - Journal of Physics A: Mathematical and Theoretical Y1 - 2021 U6 - https://doi.org/10.1088/1751-8121/abf2ec VL - 54 SP - 215601 ER - TY - JOUR A1 - Klein, Rupert A1 - Ebrahimi Viand, Roya A1 - Höfling, Felix A1 - Delle Site, Luigi T1 - Nonequilibrium induced by reservoirs: Physico-mathematical model and numerical tests JF - Advances Theory and Simulation Y1 - 2021 U6 - https://doi.org/10.1002/adts.202100071 VL - 4 SP - 2100071 ER - TY - JOUR A1 - Gholami, Abbas A1 - Höfling, Felix A1 - Klein, Rupert A1 - Delle Site, Luigi T1 - Thermodynamic relations at the coupling boundary in adaptive resolution simulations for open systems JF - Advances Theory and Simulation Y1 - 2021 U6 - https://doi.org/10.1002/adts.202000303 VL - 4 SP - 2000303 ER - TY - JOUR A1 - Mokhtari, Zahra A1 - Patterson, Robert I. A. A1 - Höfling, Felix T1 - Spontaneous trail formation in populations of auto-chemotactic walkers JF - New Journal of Physics Y1 - 2022 U6 - https://doi.org/10.1088/1367-2630/ac43ec VL - 24 SP - 013012 ER - TY - CHAP A1 - Clausecker, Robert A1 - Kaiser, Benjamin T1 - Sliding Tile Puzzles T2 - Proceedings of SAT Competition 2021 : Solver and Benchmark Descriptions Y1 - 2021 UR - http://hdl.handle.net/10138/333647 SP - 57 ER - TY - JOUR A1 - Rodrigues Pela, Ronaldo A1 - Hsiao, Ching-Lien A1 - Hultman, Lars A1 - Birch, Jens A1 - Gueorguiev, Gueorgui Kostov T1 - Electronic and optical properties of core-shell InAlN nanorods: a comparative study via LDA, LDA-1/2, mBJ, HSE06, G0W0 and BSE methods JF - Physical Chemistry Chemical Physics Y1 - 2024 U6 - https://doi.org/10.1039/D3CP05295H VL - 26 SP - 7504 EP - 7514 PB - Royal Society of Chemistry ER - TY - JOUR A1 - Juhasz, Anett A1 - Serra, Uneri Haymana A1 - Lakatos, Csilla A1 - Vadkerti, Bence A1 - Ragyanszki, Anita A1 - Farkas, Odon A1 - Keki, Sandor A1 - Nagy, Lajos T1 - The kinetics of uncatalyzed and catalyzed urethane forming reactions of aliphatic diisocyanates with butan-1-ol JF - New J. Chem. N2 - The kinetics of the urethane forming reactions of hexamethylene diisocyanate (HDI), 4,4′-dicyclohexyl-methane-diisocyanate (HMDI) and isophorone diisocyanate (IPDI) with butan-1-ol were systematically studied by electrospray ionization mass spectrometry (ESI-MS) in the off-line mode. The reactions were performed in toluene solution in the temperature range of 50–80 °C and perdeuterated butan-1-ol was used for quenching the reaction. The butan-1-ol was employed in high excess to diisocyanates to obtain pseudo first-order rate coefficients. For rendering the kinetics, a simple A → B → C consecutive model was applied and found to adequately describe the observed kinetic behaviors. The corresponding rate coefficients were determined and reactivities of the diisocyanates were found to decrease in the order HDI > IPDI > HMDI. Furthermore, it was observed that the second isocyanate group in HDI, due to the ring formation by intramolecular hydrogen bonds, reacted faster with butan-1-ol after the first isocyanate moiety had reacted. The formation of hydrogen bonding rings was also confirmed by DFT calculations. However, the reactivity of the second isocyanate moiety (after the first one has reacted) did not change significantly in the case of HMDI. From the temperature dependences the apparent activation parameters such as the pre-exponential factors and activation energies were determined. In addition, the reactions were also studied at 80 °C in the presence of tin(II)-2-ethylhexanoate at different concentrations and a mechanism was proposed for the catalytic process. Y1 - 2023 U6 - https://doi.org/10.1039/d3nj02747c VL - 47 SP - 16096 EP - 16107 ER - TY - JOUR A1 - Ji, Hongchen A1 - Ragyanszki, Anita A1 - Fournier, Rene A. T1 - Machine learning estimation of reaction energy barriers JF - Computational and Theoretical Chemistry N2 - We describe a machine learning approach to approximate reaction energy barriers (E), requiring as input only estimates of geometry and energies of reactants and products. Using the dataset of Grambow, Pattanaik, and Green [Sci. Data 7 (1 3 7) (2020)] for reactions involving seven or fewer non-hydrogen atoms, 300 reaction features are computed, and an estimate of E is obtained by fitting a Kernel Ridge Regression (KRR) model with Laplacian kernel to a subset of Density Functional Theory reaction barriers. Our main interest is small energy barriers with the goal of modeling reactions in the interstellar medium and circumstellar envelope. We omitted reactions with E > 40 kcal mol−1 to obtain a subset of 5,276 reactions for 5-fold cross-validation. For this set, the KRR model predicts E with a mean absolute error of 4.13 kcal mol−1 and a root-mean square error of 6.02 kcal mol−1. Y1 - 2023 U6 - https://doi.org/10.1016/j.comptc.2023.114332 VL - 1229 SP - 114332 ER - TY - CHAP A1 - Christgau, Steffen A1 - Everingham, Dylan A1 - Mikolajczak, Florian A1 - Schelten, Niklas A1 - Schnor, Bettina A1 - Schroetter, Max A1 - Stabernack, Benno A1 - Steinert, Fritjof T1 - Enabling Communication with FPGA-based Network-attached Accelerators for HPC Workloads T2 - Proceedings of the SC'23 Workshops of The International Conference on High Performance Computing, Network, Storage, and Analysis, SC-W 2023, Denver, CO, USA, November 12-17, 2023 N2 - The use of stand-alone, network-coupled Field Programmable Gate Array (FPGA) accelerators is intended to significantly increase the energy efficiency of HPC applications and thus also of HPC data centers. A loose coupling between the nodes of the HPC data center and the FPGAs is established through the high-speed network of the data center. This allows greater flexibility in combining different nodes and accelerators. Both the resulting energy savings and the increased flexibility through the network connection, enable the economical use of FPGAs. This work presents a communication stack to integrate the so-called Network-attached Accelerator (NAA) into the HPC data center. A low-level Remote Direct Memory Access (RDMA) Application Programming Interface (API) and a high-level Remote Procedure Call (RPC) API is designed on top of the RDMA over Converged Ethernet v2 (RoCEv2) communication stack. The experimental results over 100 Gbps RoCEv2 show that our design and implementation deliver performance close to the theoretical maximum. Y1 - 2023 U6 - https://doi.org/10.1145/3624062.3624540 SP - 530 EP - 538 PB - ACM ER - TY - JOUR A1 - Höfling, Felix A1 - Dietrich, Siegfried T1 - Structure of liquid–vapor interfaces: perspectives from liquid state theory, large-scale simulations, and potential grazing-incidence X-ray diffraction JF - The Journal of Chemical Physics N2 - Grazing-incidence X-ray diffraction (GIXRD) is a scattering technique which allows one to characterize the structure of fluid interfaces down to the molecular scale, including the measurement of the surface tension and of the interface roughness. However, the corresponding standard data analysis at non-zero wave numbers has been criticized as to be inconclusive because the scattering intensity is polluted by the unavoidable scattering from the bulk. Here we overcome this ambiguity by proposing a physically consistent model of the bulk contribution which is based on a minimal set of assumptions of experimental relevance. To this end, we derive an explicit integral expression for the background scattering, which can be determined numerically from the static structure factors of the coexisting bulk phases as independent input. Concerning the interpretation of GIXRD data inferred from computer simulations, we account also for the finite sizes of the bulk phases, which are unavoidable in simulations. The corresponding leading-order correction beyond the dominant contribution to the scattered intensity is revealed by asymptotic analysis, which is characterized by the competition between the linear system size and the X-ray penetration depth in the case of simulations. Specifically, we have calculated the expected GIXRD intensity for scattering at the planar liquid--vapor interface of Lennard-Jones fluids with truncated pair interactions via extensive, high-precision simulations. The reported data cover interfacial and bulk properties of fluid states along the whole liquid--vapor coexistence line. A sensitivity analysis demonstrates the robustness of our findings concerning the detailed definition of the mean interface position. We conclude that previous claims of an enhanced surface tension at mesoscopic scales are amenable to unambiguous tests via scattering experiments. Y1 - 2024 U6 - https://doi.org/10.1063/5.0186955 VL - 160 SP - 104107 ER - TY - CHAP A1 - Kaiser, Benjamin A1 - Clausecker, Robert A1 - Mavroskoufis, Michael T1 - Prioritised Unit Propagation by Partitioning the Watch Lists T2 - Proceedings of the 14th International Workshop on Pragmatics of SAT co-located with the 26th International Conference on Theory and Applications of Satisfiability Testing (SAT 2023) N2 - Conflict Driven Clause Learning (CDCL) SAT solvers spend most of their execution time iterating through clauses in unit propagation. Efficient implementations of unit propagation mostly rely on the two watched literals (TWL) scheme, a specialised data structure watching two literals per clause to prevent as many clause lookups as possible. In this paper, we present Priority Propagation (PriPro)—a minimally invasive method to adapt unit propagation in existing SAT solvers. With PriPro the traditional TWL scheme is partitioned to allow for rearranging the order in which clauses are examined. This is used to achieve a prioritisation of certain clauses. Using PriPro in combination with a dynamic heuristic to prioritise resolvents from recent conflicts, the effectiveness of unit propagation can be increased. In the state-of-the-art CDCL SAT solver CaDiCaL modified to use PriPro, we obtained a 5–10 % speedup on the SAT Competition 2021 benchmark set in a fair comparison with the unmodified CaDiCaL. Y1 - 2023 UR - https://ceur-ws.org/Vol-3545/paper2.pdf VL - 3545 SP - 14 EP - 34 PB - CEUR Workshop Proceedings ER - TY - JOUR A1 - Policht, Veronica R. A1 - Mittenzwey, Henry A1 - Dogadov, Oleg A1 - Katzer, Manuel A1 - Villa, Andrea A1 - Li, Qiuyang A1 - Kaiser, Benjamin A1 - Ross, Aaron M. A1 - Scotognella, Francesco A1 - Zhu, Xiaoyang A1 - Knorr, Andreas A1 - Selig, Malte A1 - Cerullo, Giulio A1 - Dal Conte, Stefano T1 - Time-domain observation of interlayer exciton formation and thermalization in a MoSe2/WSe2 heterostructure JF - Nature Communications N2 - Vertical heterostructures of transition metal dichalcogenides (TMDs) host interlayer excitons with electrons and holes residing in different layers. With respect to their intralayer counterparts, interlayer excitons feature longer lifetimes and diffusion lengths, paving the way for room temperature excitonic optoelectronic devices. The interlayer exciton formation process and its underlying physical mechanisms are largely unexplored. Here we use ultrafast transient absorption spectroscopy with a broadband white-light probe to simultaneously resolve interlayer charge transfer and interlayer exciton formation dynamics in a MoSe2/WSe2 heterostructure. We observe an interlayer exciton formation timescale nearly an order of magnitude (~1 ps) longer than the interlayer charge transfer time (~100 fs). Microscopic calculations attribute this relative delay to an interplay of a phonon-assisted interlayer exciton cascade and thermalization, and excitonic wave-function overlap. Our results may explain the efficient photocurrent generation observed in optoelectronic devices based on TMD heterostructures, as the interlayer excitons are able to dissociate during thermalization. Y1 - 2023 U6 - https://doi.org/10.1038/s41467-023-42915-x VL - 14 SP - 1 EP - 9 PB - Springer Nature ER - TY - CHAP A1 - Skoblin, Viktor A1 - Höfling, Felix A1 - Christgau, Steffen T1 - Gaining Cross-Platform Parallelism for HAL’s Molecular Dynamics Package using SYCL T2 - 29. PARS-Workshop 2023 N2 - Molecular dynamics simulations are one of the methods in scientific computing that benefit from GPU acceleration. For those devices, SYCL is a promising API for writing portable codes. In this paper, we present the case study of HAL’s MD package that has been successfully migrated from CUDA to SYCL. We describe the different strategies that we followed in the process of porting the code. Following these strategies, we achieved code portability across major GPU vendors. Depending on the actual kernels, both significant performance improvements and regressions are observed. As a side effect of the migration process, we obtained impressing speedups also for execution on CPUs. Y1 - 2023 SN - 0177-0454 VL - 36 ER - TY - JOUR A1 - Clausecker, Robert A1 - Lemire, Daniel T1 - Transcoding unicode characters with AVX-512 instructions JF - Software: Practice and Experience N2 - Intel includes in its recent processors a powerful set of instructions capable of processing 512-bit registers with a single instruction (AVX-512). Some of these instructions have no equivalent in earlier instruction sets. We leverage these instructions to efficiently transcode strings between the most common formats: UTF-8 and UTF-16. With our novel algorithms, we are often twice as fast as the previous best solutions. For example, we transcode Chinese text from UTF-8 to UTF-16 at more than 5 GiB s−1 using fewer than 2 CPU instructions per character. To ensure reproducibility, we make our software freely available as an open-source library. Our library is part of the popular Node.js JavaScript runtime. Y1 - 2023 U6 - https://doi.org/10.1002/spe.3261 VL - 53 IS - 12 SP - 2430 EP - 2462 PB - John Wiley & Sons Ltd. ER - TY - JOUR A1 - Gholami, Masoud A1 - Schintke, Florian T1 - CAWL: A Cache-aware Write Performance Model of Linux Systems JF - arXiv Y1 - 2023 U6 - https://doi.org/10.48550/arXiv.2306.05701 SP - 1 EP - 22 ER - TY - JOUR A1 - Schintke, Florian A1 - De Mecquenem, Ninon A1 - Guarino, Vanessa Emanuela A1 - Hilbrich, Marcus A1 - Lehmann, Fabian A1 - Sattler, Rebecca A1 - Sparka, Jan Arne A1 - Speckhard, Daniel A1 - Stolte, Hermann A1 - Vu, Anh Duc A1 - Leser, Ulf T1 - Validity Constraints for Data Analysis Workflows JF - arXiv Y1 - 2023 U6 - https://doi.org/10.48550/arXiv.2305.08409 SP - 1 EP - 28 ER - TY - JOUR A1 - Rodrigues Pela, Ronaldo A1 - Vona, Cecilia A1 - Lubeck, Sven A1 - Alex, Ben A1 - Gonzalez Oliva, Ignacio A1 - Draxl, Claudia T1 - Critical assessment of G0W0 calculations for 2D materials: the example of monolayer MoS2 JF - npj Comput. Mater. Y1 - 2024 U6 - https://doi.org/10.1038/s41524-024-01253-2 VL - 10 SP - 77 ER - TY - JOUR A1 - Charron, Nicholas A1 - Musil, Félix A1 - Guljas, Andrea A1 - Chen, Yaoyi A1 - Bonneau, Klara A1 - Pasos-Trejo, Aldo A1 - Jacopo, Venturin A1 - Daria, Gusew A1 - Zaporozhets, Iryna A1 - Krämer, Andreas A1 - Templeton, Clark A1 - Atharva, Kelkar A1 - Durumeric, Aleksander A1 - Olsson, Simon A1 - Pérez, Adrià A1 - Majewski, Maciej A1 - Husic, Brooke A1 - Patel, Ankit A1 - De Fabritiis, Gianni A1 - Noé, Frank A1 - Clementi, Cecilia T1 - Navigating protein landscapes with a machine-learned transferable coarse-grained model JF - Nature Chemistry N2 - The most popular and universally predictive protein simulation models employ all-atom molecular dynamics (MD), but they come at extreme computational cost. The development of a universal, computationally efficient coarse-grained (CG) model with similar prediction performance has been a long-standing challenge. By combining recent deep learning methods with a large and diverse training set of all-atom protein simulations, we here develop a bottom-up CG force field with chemical transferability, which can be used for extrapolative molecular dynamics on new sequences not used during model parametrization. We demonstrate that the model successfully predicts folded structures, intermediates, metastable folded and unfolded basins, and the fluctuations of intrinsically disordered proteins while it is several orders of magnitude faster than an all-atom model. This showcases the feasibility of a universal and computationally efficient machine-learned CG model for proteins. Y1 - 2025 U6 - https://doi.org/10.1038/s41557-025-01874-0 VL - 17 SP - 1284 EP - 1292 ER - TY - JOUR A1 - Krishnadas, Anirudh A1 - Charron, Nicolas A1 - Fournier, Rene T1 - Melting Transitions in Small Aluminum Clusters Simulated with Energies Approaching DFT Accuracy. JF - ACS Publications- Journal of Chemical Theory and Computation N2 - We describe a computational framework for modelling melting-like transitions in atomic clusters that combines first-principles energy calculations, global optimization, and machine-learned interatomic potentials. A diverse set of configurations is generated by global optimization, and energies are calculated by Density Functional Theory. The energies are fitted to an accuracy of 10 meV/atom or better with an Allegro E(3)-equivariant neural network potential. The model allows efficient parallel tempering Monte Carlo simulations with near DFT-level accuracy. This methodology was validated by simulating Na_20 and comparing it to earlier experimental and computational results. We used it to study melting-like transitions in Al_n+ clusters (n=9 to 16), and Al_n and Al_n^- (n=12, 13,14). The simulated heat capacity of these clusters, in particular Al_16+, are in qualitative agreement with experiments. The melting point of Al_n+ clusters with n=11-16 are well above the bulk melting point (934 K). The closed-shell Al_13- species has an exceptionally high melting point, close to 2100 K. Y1 - 2025 ER - TY - JOUR A1 - Krishnadas, Anirudh A1 - Moshi, Maryam A1 - Quintana, Ramon Alain Miranda A1 - Fournier, Rene T1 - Geometric Features and a Neural Network Classifier for Detecting Melting-Like Transitions in Clusters. JF - AIP Publications - The Journal of Chemical Physics N2 - Melting-like transitions in clusters are normally identified by a peak in the heat capacity curve C(T ) at T = Tc. Computing C(T ) requires costly simulations with millions of steps. We discuss four easily calculated functions of temperature that help detect and characterize melting-like transitions. The first, f1 (or WU ), is the width of the potential energy distribution which shows an abrupt increase near Tc. The other three are statistics of the ordered set of N(N − 1)/2 interatomic distances rij: (i) f2 is a measure of dissimilarity to the lowest energy configuration, or global minimum; (ii) f3 is the effective number of rij’s found in a small interval centered around (r1 + r2)/2 where r1, r2 are the positions of the first two peaks in the pair distribution function; and (iii) f4 is a measure of non-uniformity in the distribution of the ri j’s. Numerical tests with empirical potentials that model three types of bonding (van der Waals, covalent, and metallic) show that f1, f2, f3, and f4 produce estimates for the middle of the melting region in general agreement with Tc. An Artificial Neural Network (ANN) classifier that takes, as inputs, f2, f3, and many variants of f4, is used to calculate the solid fraction FS(T) and find the solid-liquid coexistence region between freezing and melting temperatures, [Tf , Tm]. Inflection points in f3(T ) and FS(T ) are very sensitive indicators of phase transitions. Estimates of Tc obtained from them converge one to three orders of magnitude faster, in simulation time, than those obtained with C(T ). Y1 - 2025 ER - TY - JOUR A1 - Clausecker, Robert A1 - Lemire, Daniel A1 - Schintke, Florian T1 - Faster Positional‐Population Counts for AVX2, AVX‐512, and ASIMD JF - Concurrency and Computation: Practice and Experience Y1 - 2025 U6 - https://doi.org/10.1002/cpe.70435 SN - 1532-0626 VL - 37 IS - 27-28 PB - Wiley ER - TY - JOUR A1 - Hölter, Arne A1 - Lemke, Mathias A1 - Weinzierl, Stefan A1 - Stein, Lewin T1 - Non-Reflecting Characteristic Boundary Conditions for Adjoint Time-Domain Acoustic Simulations JF - Journal of Theoretical and Computational Acoustics N2 - Accurate acoustic simulations in the free field require non-reflective boundary conditions to suppress spurious reflections at the computational domain boundaries. Although several characteristic-based formulations for direct (forward) simulations have been proposed in recent decades, the adjoint formulations of such characteristic-based boundary conditions (CBCs) have received limited atten- tion in the literature and lack a comprehensive analysis. This paper presents the derivation and evaluation of adjoint CBCs complementing the existing direct CBCs. Both the forward and adjoint CBCs are applied to the (nonlinear) Euler equations and linear acoustic equations in time-domain simulations. In this manner, the CBCs are investigated and subsequently compared to assess their respective accuracy and consistency. The CBCs were implemented using both a single-point and a zonal approach, with the former optionally combined with a sponge layer. Both approaches yielded comparable results in direct and adjoint simulations, while the zonal CBC exhibited improved ac- curacy at lower frequencies. Across the evaluated frequency range of approximately 350 – 5600 Hz, spurious reflections were attenuated by up to −70dB in both forward and adjoint cases, demon- strating the effectiveness and consistency of the proposed boundary treatment. Y1 - 2025 ER - TY - JOUR A1 - Raharinirina, Nomenjanahary Alexia A1 - Sunkara, Vikram A1 - von Kleist, Max A1 - Fackeldey, Konstantin A1 - Weber, Marcus T1 - Multi-Input data ASsembly for joint Analysis (MIASA): A framework for the joint analysis of disjoint sets of variables JF - PLOS ONE Y1 - 2024 U6 - https://doi.org/10.1371/journal.pone.0302425 VL - 19 IS - 5 PB - Public Library of Science ER - TY - JOUR A1 - Rodrigues Pelá, Ronaldo A1 - Draxl, Claudia T1 - Speeding up all-electron real-time TDDFT demonstrated by the exciting package JF - Comput. Phys. Commun. Y1 - 2024 U6 - https://doi.org/10.1016/j.cpc.2024.109292 VL - 304 SP - 109292 ER - TY - JOUR A1 - Höfling, Felix A1 - Straube, Arthur T1 - Langevin equations and a geometric integration scheme for the overdamped limit of rotational Brownian motion of axisymmetric particles JF - Physical Review Research N2 - The translational motion of anisotropic or self-propelled colloidal particles is closely linked with the particle’s orientation and its rotational Brownian motion. In the overdamped limit, the stochastic evolution of the orientation vector follows a diffusion process on the unit sphere and is characterized by an orientation-dependent (“multiplicative”) noise. As a consequence, the corresponding Langevin equation attains different forms depending on whether Itō’s or Stratonovich’s stochastic calculus is used. We clarify that both forms are equivalent and derive them in a top-down approach from a geometric construction of Brownian motion on the unit sphere, based on infinitesimal random rotations. Our approach suggests further a geometric integration scheme for rotational Brownian motion, which preserves the normalization constraint of the orientation vector exactly. We show that a simple implementation of the scheme, using Gaussian random rotations, converges weakly at order 1 of the integration time step, and we outline an advanced variant of the scheme that is weakly exact for an arbitrarily large time step. Due to a favorable prefactor of the discretization error, already the Gaussian scheme allows for integration time steps that are one order of magnitude larger compared to a commonly used algorithm for rotational Brownian dynamics simulations based on projection on the constraining manifold. For torques originating from constant external fields, we prove by virtue of the Fokker-Planck equation that the constructed diffusion process satisfies detailed balance and converges to the correct equilibrium distribution. The analysis is restricted to time-homogeneous rotational Brownian motion (i.e., a single rotational diffusion constant), which is relevant for axisymmetric particles and also chemically anisotropic spheres, such as self-propelled Janus particles. Y1 - 2025 U6 - https://doi.org/10.1103/wzdn-29p4 VL - 7 SP - 043034 ER - TY - GEN A1 - Schintke, Florian A1 - Greve, Nico A1 - de Cuveland, Jan ED - Friese, Volker ED - Gasik, Piotr ED - Selyuzhenkov, Ilya T1 - Recent Flesnet developments and work in progress T2 - CBM Progress Report 2023 Y1 - 2024 U6 - https://doi.org/10.15120/GSI-2024-00765 SP - 132 PB - GSI Helmholtzzentrum für Schwerionenforschung GmbH ER - TY - CHAP A1 - Witzke, Joel A1 - Lößer, Ansgar A1 - Bountris, Vasilis A1 - Schintke, Florian A1 - Scheuermann, Björn T1 - I/O of Scientific Workflows Monitored in Detail T2 - 20th IEEE International Conference on e-Science, e-Science 2024, Osaka, Japan, September 16-20, 2024 Y1 - 2024 U6 - https://doi.org/10.1109/E-SCIENCE62913.2024.10678728 N1 - Best Poster Award SP - 1 EP - 2 ER - TY - JOUR A1 - Witzke, Joel A1 - Lößer, Ansgar A1 - Bountris, Vasilis A1 - Schintke, Florian A1 - Scheuermann, Björn T1 - Low-level I/O Monitoring for Scientific Workflows JF - CoRR Y1 - 2024 U6 - https://doi.org/10.48550/ARXIV.2408.00411 VL - abs/2408.00411 SP - 1 EP - 10 ER - TY - JOUR A1 - Fritsch, Daniel A1 - Schorr, Susan T1 - Disorder induced band gap lowering in kesterite type Cu2ZnSnSe4 and Ag2ZnSnSe4: a first-principles and special quasirandom structures investigation JF - Journal of Physics: Condensed Matter N2 - Abstract Quaternary chalcogenides, i.e. Cu2ZnSnS4, crystallising in the kesterite crystal structure have already been demonstrated as potential building blocks of thin film solar cells, containing only abundant elements and exhibiting power conversion efficiencies of about 14.9% so far. However, due to the potential presence of several structurally similar polymorphs, the unequivocal identification of their ground state crystal structures required the application of more elaborate neutron diffraction experiments. One particular complication arose from the later identified Cu–Zn disorder, present in virtually all thin film samples. Subsequently, it has been shown experimentally that this unavoidable Cu–Zn disorder leads to a band gap lowering in the respective samples. Additional theoretical investigations, mostly based on Monte-Carlo methods, tried to understand the atomistic origin of this disorder induced band gap lowering. Here, we present theoretical results from first-principles calculations based on density functional theory for the disorder induced band gap lowering in kesterite Cu2ZnSnSe4 and Ag2ZnSnSe4, where the Cu–Zn and Ag–Zn disorder is modelled via a supercell approach and special quasirandom structures. Results of subsequent analyses of structural, electronic, and optical properties are discussed with respect to available experimental results, and will provide additional insight and knowledge towards the atomistic origin of the observed disorder induced band gap lowering in kesterite type materials. Y1 - 2024 U6 - https://doi.org/10.1088/1361-648X/ad52de SN - 0953-8984 VL - 36 IS - 37 PB - IOP Publishing ER - TY - CHAP A1 - Kramer, Tobias A1 - Läuter, Matthias T1 - Benchmarking the rotating jet model of cometary activity with the trajectory of comet 67P/Churyumov-Gerasimenko T2 - EPSC Abstracts N2 - An important tool to assess the composition and the spatial origin of cometary material is the analysis of its trajectory reflecting gravitational acceleration due to solar system bodies complemented by non-gravitational accelerations (NGA). Y1 - 2024 U6 - https://doi.org/10.5194/epsc2024-207 VL - 17 ER - TY - JOUR A1 - Attree, Nicholas A1 - Gutiérrez, Pedro A1 - Groussin, Olivier A1 - Bürger, Johanna A1 - Keller, Horst Uwe A1 - Kramer, Tobias A1 - LASAGNI MANGHI, RICCARDO A1 - Läuter, Matthias A1 - Lemos, Pablo A1 - Markkanen, Johannes A1 - Marschall, Raphael A1 - Schuckart, Christian T1 - Varying water activity and momentum transfer on comet 67P/Churyumov-Gerasimenko from its non-gravitational forces and torques JF - Astronomy and Astrophysics N2 - Aims. We investigate the ability of a simultaneous fitting of comet 67P/Churyumov-Gerasimenko’s non-gravitational forces, torques, and total water-outgassing rate, as observed by Rosetta, to constrain complex thermophysical models of cometary material. Methods. We extend the previous work of fitting geographically defined surface outgassing models to the Rosetta observations by testing the effects of a more detailed geomorphological mapping, the resolution of the shape-model used, self-heating by neighbouring facets on the shape-model, thermal inertia in the outgassing solution, and the variation in the momentum coupling between the gas and the nucleus. We also directly compare the non-gravitational acceleration curves available in the literature. Results. We correct an error in the calculation of pole-orientation in the previous paper. We find that, under the assumptions of the model, non-gravitational forces and torques are driven by water sublimation from the nucleus, thermal inertia and self-heating have only minor effects, spatially uniform activity cannot explain 67P’s non-gravitational dynamics, spatially uniform momentum transfer cannot explain 67P’s non-gravitational dynamics, and different terrain types have different instantaneous responses to insolation. Conclusions. Consolidated terrain facing south on 67P/Churyumov-Gerasimenko has a high outgassing flux, a steep response to insolation, and a large gas momentum transfer coefficient. Instead, that facing north behaves differently, producing little to no water outgassing, and with a lower momentum transfer efficiency. Dusty terrain also has a lower outgassing rate and momentum transfer efficiency, and either depletes its volatile component or is buried in fall-back as the comet approaches the Sun. Momentum transfer appears correlated with insolation, likely due to an increased enhancement in the gas temperature as the dust it flows through is heated. Y1 - 2024 U6 - https://doi.org/10.1051/0004-6361/202450728 VL - 690 SP - A82 ER - TY - CHAP A1 - Attree, Nicholas A1 - Gutiérrez, Pedro A1 - Groussin, Olivier A1 - Bürger, Johanna A1 - Keller, Horst Uwe A1 - Kramer, Tobias A1 - Lasagni Manghi, Riccardo A1 - Läuter, Matthias A1 - Lemos, Pablo A1 - Markkanen, Johannes A1 - Marschall, Raphael A1 - Schuckart, Christian T1 - The Results of ISSI Team #547: Understanding the Activity of Comets Through 67P's Dynamics T2 - EPSC Abstracts N2 - Understanding cometary activity gives us an insight into the materials properties, and therefore formation and evolution processes of these relatively pristine protoplanetary objects. We will present the results of an International Space Science Institute project to investigate the phenomenon through the effects of the outgassing activity on the orbit and spin-state of comet 67P/Churymov-Gerasimenko, e.g. its non-gravitational dynamics. This International Team gathered experts in orbital dynamics and trajectory reconstruction together with thermophysical modellers and comet observationalists, in order to compare the available extractions of 67P’s non-gravitational acceleration (NGA) from its trajectory. The team then fitted a combination of the NGA, the non-gravitational torque (NGT), and the total water-outgassing rate with a thermophysical activity model. The results of this model will be presented. In particular, it was found that: non-gravitational forces and torques are driven by water sublimation from the nucleus; thermal inertia and self-heating have only minor effects; spatially uniform activity cannot explain 67P's non-gravitational dynamics; spatially uniform momentum transfer cannot explain 67P's non-gravitational dynamics; and different terrain types have different instantaneous responses to insolation. The implications of these findings for the modelling of cometary material and the variety of surface types seen on 67P will be discussed. Y1 - 2024 U6 - https://doi.org/10.5194/epsc2024-82 VL - 17 ER - TY - JOUR A1 - Roy, Sutapa A1 - Höfling, Felix T1 - Critical surface adsorption of confined binary liquids with locally conserved mass and composition JF - Molecular Physics N2 - Close to a solid surface, the properties of a fluid deviate significantly from their bulk values. In this context, we study the surface adsorption profiles of a symmetric binary liquid confined to a slit pore by means of molecular dynamics simulations; the latter naturally entails that mass and concentration are locally conserved. Near a bulk consolute point, where the liquid exhibits a demixing transition with the local concentration as the order parameter, we determine the order parameter profiles and characterise the relevant critical scaling behaviour, in the regime of strong surface attraction, for a range of pore widths and temperatures. The obtained order parameter profiles decay monotonically near the surfaces, also in the presence of a pronounced layering in the number density. Overall, our results agree qualitatively with recent theoretical predictions from a mesoscopic field-theoretical approach for the canonical ensemble. Y1 - 2024 U6 - https://doi.org/10.1080/00268976.2024.2391998 VL - 122 IS - 21-22 SP - e2391998 ER - TY - THES A1 - Jami, Masoud T1 - Optimizing Checkpoint/Restart and Input/Output for Large Scale Applications Y1 - 2024 UR - https://doi.org/10.18452/29985 U6 - https://doi.org/10.18452/29985 PB - Humboldt-Universität zu Belin ER - TY - JOUR A1 - Marcelli, Giorgia A1 - Bottinelli Montandon, Tecla A1 - Ebrahimi Viand, Roya A1 - Höfling, Felix T1 - Fluid flow inside slit-shaped nanopores: the role of surface morphology at the molecular scale JF - The Journal of Chemical Physics N2 - Non-equilibrium molecular dynamics (NEMD) simulations of fluid flow have highlighted the peculiarities of nanoscale flows compared to classical fluid mechanics; in particular, boundary conditions can deviate from the no-slip behavior at macroscopic scales. For fluid flow in slit-shaped nanopores, we demonstrate that surface morphology provides an efficient control on the slip length, which approaches zero when matching the molecular structures of the pore wall and the fluid. Using boundary-driven, energy-conserving NEMD simulations with a pump-like driving mechanism, we examine two types of pore walls—mimicking a crystalline and an amorphous material—that exhibit markedly different surface resistances to flow. The resulting flow velocity profiles are consistent with Poiseuille theory for incompressible, Newtonian fluids when adjusted for surface slip. For the two pores, we observe partial slip and no-slip behavior, respectively. The hydrodynamic permeability corroborates that the simulated flows are in the Darcy regime. However, the confinement of the fluid gives rise to an effective viscosity below its bulk value; wide pores exhibit a crossover between boundary and bulk-like flows. In addition, the thermal isolation of the flow causes a linear increase in fluid temperature along the flow, which we relate to strong viscous dissipation and heat convection, utilizing conservation laws of fluid mechanics. Noting that the investigated fluid model does not form droplets, our findings challenge the universality of previously reported correlations between slippage, solvophobicity, and a depletion zone. Furthermore, they underscore the need for molecular-scale modeling to accurately capture the fluid dynamics near boundaries and in nanoporous materials, where macroscopic models may not be applicable. Y1 - 2025 U6 - https://doi.org/10.1063/5.0246573 VL - 162 SP - 104101 ER - TY - JOUR A1 - Zhong, Xin A1 - Höfling, Felix A1 - John, Timm T1 - Hydrogen diffusion in garnet: insights from atomistic simulations JF - Geochemistry Geophysics Geosystems N2 - Garnet has been widely used to decipher the pressure-temperature-time history of rocks, but its physical properties such as elasticity and diffusion are strongly affected by trace amounts of hydrogen. Experimental measurements of H diffusion in garnet are limited to room pressure. We use atomistic simulations to study H diffusion in perfect and defective garnet lattices, focusing on protonation defects at the Si and Mg sites, which are shown to be energetically favored. Transient trapping of H renders ab-initio simulations of H diffusion computationally challenging, which is overcome with machine learning techniques by training a deep neural network that encodes the interatomic potential. Our results from such deep potential molecular dynamics (DeePMD) simulations show high mobility of hydrogen in defect-free garnet lattices, whereas H diffusivity is significantly diminished in defective lattices. Tracer simulations focusing on H alone highlight the vital role of atomic vibrations of heavier atoms like Mg on the release of H atoms. Two regimes of H diffusion are identified: a diffuser-dominated regime at high hydrogen content with low activation energies due to saturation of vacancies by hydrogen, and a vacancy-dominated regime at low hydrogen content with high activation energies due to trapping of H atoms at vacancy sites. These regimes account for experimental observations, such as a H-concentration dependent diffusivity and the discrepancy in activation energy between deprotonation and D-H exchange experiments. This study underpins the crucial role of vacancies in H diffusion and demonstrates the utility of machine-learned interatomic potentials in studying kinetic processes in the Earth's interior. Y1 - 2025 U6 - https://doi.org/10.1029/2024GC011951 VL - 26 SP - e2024GC011951 ER - TY - JOUR A1 - Caruso, Fabio A1 - Sentef, Michael A1 - Attaccalite, Claudio A1 - Bonitz, Michael A1 - Draxl, Claudia A1 - De Giovannini, Umberto A1 - Eckstein, Martin A1 - Ernstorfer, Ralph A1 - Fechner, Michael A1 - Grüning, Myrta A1 - Hübener, Hannes A1 - Joost, Jan-Philip A1 - Juraschek, Dominik A1 - Karrasch, Christoph A1 - Marvin Kennes, Dante A1 - Latini, Simone A1 - Lu, I-Te A1 - Neufeld, Ofer A1 - Perfetto, Enrico A1 - Rettig, Laurenz A1 - Rodrigues Pelá, Ronaldo A1 - Rubio, Angel A1 - Rudzinski, Joseph A1 - Ruggenthaler, Michael A1 - Sangalli, Davide A1 - Schüler, Michael A1 - Shallcross, Samuel A1 - Sharma, Sangeeta A1 - Stefanucci, Gianluca A1 - Werner, Philipp T1 - The 2025 Roadmap to Ultrafast Dynamics: Frontiers of Theoretical and Computational Modelling JF - J. Phys. Mater. Y1 - 2026 U6 - https://doi.org/10.1088/2515-7639/ae1165 VL - 9 IS - 1 ER - TY - GEN A1 - Ragyanszki, Anita A1 - Ji, Hongchen A1 - Fournier, Rene T1 - Understanding the Origins of Life - A Machine learning approach to estimate reaction mechanisms of biotic precursors T2 - Perspectives and challenges of future HPC installations for atomistic and molecular simulations N2 - Life as we know it is the result of billions of years of evolution; yet, understanding how the very first organisms came into existence is a challenge that has yet to be solved. One theory states that components of the first biotic molecules may not have formed on Earth. Rather, they may have initially formed in the interstellar medium (ISM) and been transported to Earth, as supported by recorded instances of organic molecules detected in space. The ISM, with its low temperatures and specific collision processes, allows for molecular stability and the formation of biotic precursors that would otherwise be unlikely in Earth's prebiotic conditions. Understanding how these molecules formed in the ISM may be the key to determining how life began. The goal of this research is to develop a new model for solving astrobiophysical problems by studying the formation mechanisms of biomolecules found in the ISM. Although such pathways have been studied individually, there has not yet been a comprehensive method to understand all the formation reactions that can occur in ISM. Several quantum chemical and numerical methods are available for finding transition states (TS) and energy barriers (E) of chemical reactions but are time-consuming and can hardly be applied to systems with more than a few atoms. Our main interest is to develop a a machine learning approach to approximate TS, and E, requiring as input only estimates of geometry and energies of reactants and products. Using a complete dataset 300 reaction features are computed, and an estimate of E is obtained by fitting a Kernel Ridge Regression (KRR) model with Laplacian kernel, and a fully connected Artificial Neural Network (ANN) to estimate reaction energy barriers. Y1 - 2024 ER - TY - GEN A1 - Ragyanszki, Anita A1 - Ji, Hongchen A1 - Fournier, Rene T1 - Understanding the Origins of Life – A Machine learning approach to estimate reaction mechanisms of biotic precursors T2 - SIMPLAIX N2 - Understanding the Origins of Life - A Machine learning approach to estimate reaction mechanisms of biotic precursors. Life as we know it is the result of billions of years of evolution; however, understanding how the very first organisms came into existence is a challenge that has yet to be solved. One theory states that components of these molecules may have formed in the interstellar medium (ISM) and been transported to Earth. The ISM, with its specific conditions, allows for molecular stability and the formation of biotic precursors that would otherwise be unlikely in Earth's prebiotic conditions. Understanding how these molecules formed in the ISM may be the key to determining how life began. The goal of this research is to develop a model for solving astrobiophysical problems by studying the formation mechanisms of biomolecules found in the ISM. Although such pathways have been studied individually, there has not yet been a comprehensive method to understand the complete reactions mechanisms. Several QM methods are available for finding transition states (TS) and energy barriers (E) of chemical reactions but are time-consuming and can hardly be applied to more complex systems. Our interest is to develop a machine learning approach to approximate TS, and E, requiring as input only estimates of geometry and energies of reactants and products. Y1 - 2024 ER - TY - CHAP A1 - Christgau, Steffen A1 - Dylan, Everingham A1 - Lübke, Max A1 - De Lucia, Marco A1 - Puhan, Danny A1 - Schelten, Niklas A1 - Schnor, Bettina A1 - Signer, Hannes A1 - Spazier, Johannes A1 - Stabernack, Benno A1 - Steinert, Fritjof A1 - Yahdzhyiev, Serhii T1 - On the Usability and Energy Efficiency of High-Level Synthesis for FPGA-based Network-Attached Accelerators T2 - 2025 IEEE International Parallel and Distributed Processing Symposium Workshops (IPDPSW) N2 - Heterogeneity in high performance computing systems is one of the most promising approaches towards more energy-efficient computing on one hand and satisfying the raising demand of global computation capacity on the other hand. Besides the well-known key components like CPUs and GPGPUs are domain-specific accelerators like TPUs, FPGAs well known for their energy efficiency. This is especially true for highly specialized use cases. Network-attached accelerators promise more scalability and flexibility for FPGA usage in HPC environments. Easy and efficient programming of those accelerators is, however, still an open issue. Based on a framework for such accelerators which enables decoupling of FPGAs from their host system, we present a workflow using High-Level Synthesis (HLS) to offload application kernels to them. We evaluate this approach against a conventional Hardware Description Language (HDL) based workflow. In addition, we introduce the energy measurement tool EMA and assess the energy efficiency of both HLS and HDL design. Y1 - 2025 U6 - https://doi.org/10.1109/IPDPSW66978.2025.00139 SP - 886 EP - 895 ER - TY - JOUR A1 - Läuter, Matthias A1 - Kramer, Tobias T1 - Rotation dynamics and torque efficiency of cometary nuclei JF - Astronomy & Astrophysics N2 - The dynamics of a rigid cometary nucleus is described by the evolutions of its center-of-mass and of its rotation state. Solar irradiation that reaches the surface of a cometary nucleus causes the sublimation of volatiles that form the coma around the nucleus. The sublimation process transfers linear momentum and rotational angular momentum from the nucleus to the surrounding space, and thus affects the dynamics via nongravitational forces and nongravitational torques. With the exception of close approaches to planets, these torques exert the dominant influence on the rotation states of cometary nuclei. The Rosetta mission 2014-2016 accompanying comet 67P/Churyumov-Gerasimenko provides the longest continuous observational data to track its rotation state. In particular, the data set encompasses the direction of the angular velocity, denoted by ω, and the angular frequency |ω|over a time period of approximately 700 days. The observed change of the rotation state is not explained by a low heat conductivity thermophysical model in combination with a homogeneous surface ice coverage of comet 67P. Spatially and/or temporally varying weights for effective active fraction with respect to a prescribed set of surface regions provide a potential solution to this problem. Here, we present a methodology for classifying the surface based on vectorial efficiency of the torque. On any cometary surface without geometric symmetry, the methodology highlights the decomposition into eight characteristic regions that encode the signs of torque efficiency with respect to all vector components. This decomposition is divided into two subsets of four regions each of which is located in one of both hemispheric regions. We analyze in detail rotation states close to lowest energy and different thermophysical models, and we discuss how the uncertainties of observations affect the model parameters. We study the occurrence of these regions for an oblate ellipsoid, a nearprolate ellipsoid, a bilobed shape, and a shape model analogous to that of comet 67P. The sensitivity analysis for comet 67P indicates that the observations constrain only one of the eight weights uniquely. The other directions are poorly constrained and show the limitation of the rotational data to determine the regional activity on comet 67P. Y1 - 2025 U6 - https://doi.org/10.1051/0004-6361/202553845 VL - 699 SP - A75 ER - TY - THES A1 - el Bahnasawy, Henry T1 - Konzeption und Entwicklung einer Plattform zur geographisch verteilten Bereitstellung von latenzkritischen Anwendungen Y1 - 2025 ER - TY - JOUR A1 - Rossi, Thomas A1 - Qiao, Lu A1 - Dykstra, Conner P. A1 - Rodrigues Pelá, Ronaldo A1 - Gnewkow, Richard A1 - Wallick, Rachel F. A1 - Burke, John H. A1 - Nicholas, Erin A1 - March, Anne-Marie A1 - Doumy, Gilles A1 - Buchholz, D. Bruce A1 - Deparis, Christiane A1 - Zuñiga-Pérez, Jesus A1 - Weise, Michael A1 - Ellmer, Klaus A1 - Fondell, Mattis A1 - Draxl, Claudia A1 - van der Veen, Renske T1 - Dynamic control of X-ray core-exciton resonances by Coulomb screening in photoexcited semiconductors JF - Communications Materials Y1 - 2025 U6 - https://doi.org/10.1038/s43246-025-00909-w VL - 6 SP - 191 ER - TY - JOUR A1 - Hawthorne, Felipe A1 - Raulino, Paulo R. E. A1 - Rodrigues Pelá, Ronaldo A1 - Woellner, Cristiano F. T1 - Efficient and Accurate Machine Learning Interatomic Potential for Graphene: Capturing Stress–Strain and Vibrational Properties JF - The Journal of Physical Chemistry C Y1 - 2025 U6 - https://doi.org/10.1021/acs.jpcc.5c03470 VL - 129 SP - 16319 EP - 16326 ER - TY - JOUR A1 - Clausecker, Robert A1 - Lemire, Daniel A1 - Schintke, Florian T1 - Faster Positional-Population Counts for AVX2, AVX-512, and ASIMD JF - CoRR Y1 - 2024 U6 - https://doi.org/10.48550/arXiv.2412.16370 VL - abs/2412.16370 SP - 1 EP - 23 ER - TY - CHAP A1 - Lößer, Ansgar A1 - Witzke, Joel A1 - Schintke, Florian A1 - Scheuermann, Björn T1 - BottleMod: Modeling Data Flows and Tasks for Fast Bottleneck Analysis T2 - Proceedings of the 16th ACM/SPEC International Conference on Performance Engineering (ICPE 2025) Y1 - 2025 U6 - http://nbn-resolving.de/urn/resolver.pl?https://doi.org/10.1145/3676151.3719382 SP - 11 EP - 18 PB - Association for Computing Machinery ER - TY - JOUR A1 - Ji, Hongchen A1 - Ragyanszki, Anita A1 - Fournier, Rene T1 - A Machine Learning and Quantum Chemistry Approach for Identifying Prebiotic Molecules in the Interstellar Medium JF - Physical Chemistry Chemical Physics N2 - The discovery of molecules in the interstellar medium (ISM) plays a key role in understanding prebiotic chemistry. Relatively few (∼250) molecules have been confirmed in the ISM, and detecting additional species is crucial for expanding our knowledge of astrochemical processes. We present a strategy for predicting possible prebiotic molecules in the ISM that combines machine learning and high-accuracy quantum chemistry calculations. Using a reaction dataset of over 153,000 possible combinations of known interstellar molecules, we applied a machine learning model to estimate reaction energy barriers and identify those with low or zero barriers that are most likely to occur in the ISM. From this screening process, 24 molecules were identified, five of which have already been observed in interstellar space. For the remaining 19 molecules, we conducted density functional theory (DFT) and coupled cluster theory calculations to determine the most stable conformers, spectroscopic parameters, and predict their detectability through spectroscopy. We present data to guide future observational searches for new interstellar species, contributing to the ongoing exploration of complex organic molecules in space and their potential role in prebiotic chemistry. Y1 - 2024 ER - TY - JOUR A1 - Rozsa, Zsofia Borbala A1 - Ragyanszki, Anita A1 - Viskolcz, Bela A1 - Szori, Milan T1 - Chemical space of the singlet C4H8O2 species. A systematic theoretical analysis on their structural and thermochemical properties JF - Computational and Theoretical Chemistry N2 - The goal of this study was to explore and define the thermodynamic properties of one of the subspaces of ‘chemical space’ using a mixture of graph theory and theoretical chemistry tools. Therefore, all possible mo- lecular structures with C4H8O2 stoichiometry were generated, considering constitutional isomers and molecular complexes. The thermodynamic properties of the obtained isomers have been obtained by G3MP2B3 protocol. The classification of the obtained isomers was simplified by using thermodynamic maps, which is an effective method for the comparison of thermodynamic stability for entities of complex molecular systems. Modern computational methods can be used to understand larger systems, which has made it possible to characterize a chemical subspace not only by selecting individual entities, but also as a whole. With this pro- cedure one can catch a glimpse into the diversity of a molecular system and predict further uses of newly discovered molecules or design molecules with predefined properties. Y1 - 2023 U6 - https://doi.org/10.1016/j.comptc.2023.114162 VL - 1225 SP - 114162 ER - TY - JOUR A1 - Ragyanszki, Anita A1 - Fiser, Bela A1 - Lee-Ruff, Edward A1 - Liebman, Joel F. T1 - Strained Small Nitrogen Heterocycles-Azabicyclobutanes and Azirines JF - ChemistrySelect N2 - Small ring nitrogen heterocycles, azabicyclobutanes and azirines, were investigated by computational methods in order to address the discrepancy between their regioisomers 1- and 2-azabicyclobutane and 1H- and 2H-azirines. Both 1-azabicyclobutane and 2H-azirine are well known synthetic starting points to larger nitrogen heterocycles whereas 2-azabicyclobutane and 1H-azirine and their derivatives have yet to be reported as isolable compounds. Calculated parameters such as structure, base strength (proton affinities), NICS values and enthalpies of formation from which strain energies are derived are reported. The destabilization of the less stable regioisomers is attributed to homoantiaromaticity in 2-azabicyclobutane and antiaromaticity in 1H-azirine. Two stereoisomers exist for 2-azabicyclobutane with the endo- stereoisomer being more stable. This phenomenon is indicative of the hydrogen bond acceptor properties of the neighboring cyclpropane and the π-bond character of the central bond in 2-azabicyclobutane. Y1 - 2023 U6 - https://doi.org/10.1002/slct.202301405 VL - 8 IS - 26 ER - TY - JOUR A1 - Groussin, Olivier A1 - Jorda, L. A1 - Attree, N. A1 - Birch, S.P.D. A1 - Bürger, Johanna A1 - Gutiérrez, Pedro A1 - Jindal, Abhinav S. A1 - Keller, H.U. A1 - Kramer, Tobias A1 - Lasagni Manghi, Riccardo A1 - Läuter, Matthias A1 - Markkanen, J. A1 - Marschall, R. A1 - Schuckart, C. T1 - Thermal environment and erosion of comet 67P/Churyumov-Gerasimenko JF - Astronomy and Astrophysics N2 - Aims. This paper focuses on how insolation affects the nucleus of comet 67P/Churyumov-Gerasimenko over its current orbit. We aim to better understand the thermal environment of the nucleus, in particular its surface temperature variations, erosion, relationship with topography, and how insolation affects the interior temperature for the location of volatile species (H2O and CO2). Methods. We have developed two thermal models to calculate the surface and subsurface temperatures of 67P over its 6.45-year orbit. The first model, with high resolution (300 000 facets), calculates surface temperatures, taking shadows and self-heating into account but ignoring thermal conductivity. The second model, with lower resolution (10 000 facets), includes thermal conductivity to estimate temperatures down to ∼3 m below the surface. Results. The thermal environment of 67P is strongly influenced by its large obliquity (52◦), which causes significant seasonal effects and polar nights. The northern hemisphere is the coldest region, with temperatures of 210–300 K. H2O is found in the first few centimetres, while CO2 is found deeper (∼2 m) except during polar night around perihelion, when CO2 accumulates near the surface. Cliffs erode 3–5 times faster than plains, forming terraces. The equatorial region receives maximum solar energy (8.5×109 J m−2 per orbit), with maximum surface temperatures of 300–350 K. On the plains, H2O is found in the first few centimetres, while CO2 is found deeper (∼2 m) and never accumulates near the surface. In the southern hemisphere, a brief intense perihelion heating raises temperatures to 350–400 K, which is followed by a 5-year polar night when surface temperatures drop to 55 K. Here H2O remains in the first few centimetres, while CO2 accumulates shallowly during polar night, enriching the region. Erosion is maximal in the southern hemisphere and concentrated on the plains, which explains the observed overall flatness of this hemisphere compared to the northern one. Over one orbit, the total energy from self-heating is 17% of the total energy budget, and 34% for thermal conduction. Our study contributes to a better understanding of the surface changes observed on 67P. Y1 - 2025 U6 - https://doi.org/10.1051/0004-6361/202452260 VL - 694 SP - A21 ER - TY - CHAP A1 - Lößer, Ansgar A1 - Schlecht, Max A1 - Schintke, Florian A1 - Witzke, Joel A1 - Weidlich, Matthias A1 - Scheuermann, Björn T1 - Fast Min-ϵ Segmented Regression using Constant-Time Segment Merging T2 - Proceedings of the 42nd International Conference on Machine Learning Y1 - 2025 UR - https://proceedings.mlr.press/v267/losser25a.html VL - 267 SP - 40312 EP - 40327 ER - TY - JOUR A1 - Agarwal, A. A1 - Greve, Nico A1 - Reinefeld, Alexander A1 - Schintke, Florian A1 - et al., T1 - Performance of the prototype Silicon Tracking System of the CBM experiment tested with heavy-ion beams at SIS18 JF - Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment Y1 - 2025 U6 - https://doi.org/10.1016/j.nima.2025.171059 SN - 0168-9002 N1 - This paper has 343 authors. For the complete list of authors use the DOI, please. VL - 1082 SP - 171059 PB - Elsevier BV ER -