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Nuclear quantum effects on the vibrational dynamics of liquid water

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arXiv 2018年

作者： Ojha, Deepak Henao, Andrés Kühne, Thomas D. Dynamics of Condensed Matter and Center for Sustainable Systems Design Department of Chemistry University of Paderborn Warburger Str. 100 PaderbornD-33098 Germany Paderborn Center for Parallel Computing Institute for Lightweight Design University of Paderborn Warburger Str. 100 PaderbornD-33098 Germany

Based on quantum-mechanical path-integral molecular dynamics simulations the impact of nuclear quantum effects on the vibrational and hydrogen bond dynamics in liquid water is investigated. The instantaneous fluctuations in the frequencies of the O-H stretch modes are calculated using the wavelet method of time series analysis, while the time scales of the vibrational spectral diffusion are determined from frequency-time correlation functions, joint probability distributions, as well as the slope of three-pulse photon echo. We find that the inclusion of nuclear quantum effects leads not only to a redshift of the vibrational frequency distribution by around 130 cm-1, but also to an acceleration of the vibrational dynamics by as much as 30%. In addition, quantum fluctuations also entail a significantly faster decay of correlation in the initial diffusive regime, which is agreement with recent vibrational echo experiments. Copyright © 2018, The Authors. All rights reserved.

关键词： Time series analysis

RsdEditor: a graphical user interface for specifying metacomputer components

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RsdEditor: a graphical user interface for specifying metacom...

Heterogeneous computing Workshop

作者： R. Baraglia D. Laforenza A. Keller A. Reinefeld CNUCE-Instituto del Consiglio Nazionale delle Ricerche Pisa Italy Paderborn Center for Parallel Computing Paderborn Germany Konrad-Zuse-Zentrum für Informationstechnik Berlin Germany

RsdEditor is a graphical user interface which produces specifications of computational resources. It is used in the RSD (Resource and Service Description) environment for specifying, registering, requesting and accessing resources and services in a metacomputer. RsdEditor was designed to be used by the administrators and users of metacomputing environments. At the administrator level, the GUI is used to describe the available computing and networking components of a metacomputer. At the user level, RsdEditor can be used to specify which characteristics of the computational resources are needed to execute a meta-application. This paper is organized as follows: it first introduces RsdEditor. It then briefly describes the RSD environment, and finally, it highlights various features and implementation issues of RsdEditor.

关键词： Graphical user interfaces Electrical capacitance tomography Data structures Tellurium Carbon capture and storage Libraries Bandwidth Delay Wide area networks Indium tin oxide

"On-the-fly" calculation of the vibrational sum-frequency generation spectrum at the air-water interface

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arXiv 2020年

作者： Ojha, Deepak Kühne, Thomas D. Dynamics of Condensed Matter and Center for Sustainable Systems Design Chair of Theoretical Chemistry Department of Chemistry Paderborn University Warburger Str. 100 Paderborn33098 Germany Paderborn Center for Parallel Computing Institute for Lightweight Design Paderborn University Warburger Str. 100 PaderbornD-33098 Germany

In the present work, we provide an electronic structure based method for the "on-the-fly" determination of vibrational sum frequency generation (v-SFG) spectra. The predictive power of this scheme is demonstrated at the air-water interface. While the instantaneous fluctuations in dipole moment are obtained using the maximally localized Wannier functions, the fluctuations in polarizability are approximated to be proportional to the second moment of Wannier functions. The spectrum henceforth obtained captures the signatures of hydrogen bond stretching, bending, as well as low-frequency librational modes. Copyright © 2020, The Authors. All rights reserved.

关键词： Electronic structure

Equation of state of atomic solid hydrogen by stochastic many-body wave function methods

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arXiv 2020年

作者： Azadi, Sam Booth, George H. Kühne, Thomas D. Department of Physics King’s College London Strand LondonWC2R 2LS United Kingdom Department of Chemistry Paderborn Center for Parallel Computing Paderborn University Paderborn33098 Germany

We report a numerical study of the equation of state of crystalline body-centered-cubic (BCC) hydrogen, tackled with a variety of complementary many-body wave function methods. These include continuum stochastic techniques of fixed-node diffusion and variational quantum Monte Carlo, and the Hilbert space stochastic method of full configuration interaction quantum Monte Carlo. In addition, periodic coupled-cluster methods were also employed. Each of these methods is underpinned with different strengths and assumptions, but their combination in order to perform reliable extrapolation to complete basis set and supercell size limits gives confidence in the final results. The methods were found to be in good agreement for equilibrium cell volumes for the system in this phase, with a lattice parameter of 3.31 Bohr. Copyright © 2020, The Authors. All rights reserved.

关键词： Equations of state

Artificial neural networks as trial wave functions for quantum Monte Carlo

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arXiv 2019年

作者： Kessler, Jan Calcavecchia, Francesco Kühne, Thomas D. Dynamics of Condensed Matter Center for Sustainable Systems Design Chair of Theoretical Chemistry University of Paderborn Warburger Str. 100 PaderbornD-33098 Germany Paderborn Center for Parallel Computing Institute for Lightweight Design University of Paderborn Warburger Str. 100 PaderbornD-33098 Germany

Inspired by the universal approximation theorem and widespread adoption of artificial neural network techniques in a diversity of fields, we propose feed-forward neural networks as general purpose trial wave functions for quantum monte carlo (QMC) simulations of many-body systems. To verify their practical success, we employ various realizations of this ansatz in QMC simulations of an exactly solvable model system of two trapped interacting particles. Finally, we use the same technique to accurately predict the binding curve of the hydrogen molecule, from first principles. Copyright © 2019, The Authors. All rights reserved.

关键词： Wave functions

Proceedings - 2010 IEEE International Conference on Networking, Architecture and Storage, NAS 2010: Preface

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Proceedings - 2010 IEEE International Conference on Networki...

Proceedings - 2010 IEEE International Conference on Networking, Architecture and Storage, NAS 2010 2010年 x-xi页

作者： Cheng, Xiuzhen Zhu, Yifeng Brinkmann, Andre Xuan, Dong George Washington University United States University of Maine United States Paderborn Center for Parallel Computing Germany Ohio-State University United States

Scalable quantum detector tomography by high-performance computing

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arXiv 2024年

作者： Schapeler, Timon Schade, Robert Lass, Michael Plessl, Christian Bartley, Tim J. Department of Physics Paderborn University Warburger Str. 100 Paderborn33098 Germany Paderborn University Warburger Str. 100 Paderborn33098 Germany Paderborn Center for Parallel Computing Paderborn University Warburger Str. 100 Paderborn33098 Germany Department for Computer Science Paderborn University Warburger Str. 100 Paderborn33098 Germany

At large scales, quantum systems may become advantageous over their classical counterparts at performing certain tasks. Developing tools to analyse these systems at the relevant scales, in a manner consistent with quantum mechanics, is therefore critical to benchmarking performance and characterising their operation. While classical computational approaches cannot perform like-for-like computations of quantum systems beyond a certain scale, classical high-performance computing (HPC) may nevertheless be useful for precisely these characterisation and certification tasks. By developing open-source customised algorithms using high-performance computing, we perform quantum tomography on a megascale quantum photonic detector covering a Hilbert space of 106. This requires finding 108 elements of the matrix corresponding to the positive operator valued measure (POVM), the quantum description of the detector, and is achieved in minutes of computation time. Moreover, by exploiting the structure of the problem, we achieve highly efficient parallel scaling, paving the way for quantum objects up to a system size of 1012 elements to be reconstructed using this method. In general, this shows that a consistent quantum mechanical description of quantum phenomena is applicable at everyday scales. More concretely, this enables the reconstruction of large-scale quantum sources, processes and detectors used in computation and sampling tasks, which may be necessary to prove their nonclassical character or quantum computational advantage. Copyright © 2024, The Authors. All rights reserved.

关键词： Tomography

Continuum extrapolation of the gradient-flowed color-magnetic correlator at 1.5 Tc 38

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Continuum extrapolation of the gradient-flowed color-magneti...

38th International Symposium on Lattice Field Theory, LATTICE 2021

作者： Altenkort, Luis Eller, Alexander M. Kaczmarek, Olaf Mazur, Lukas Moore, Guy D. Shu, Hai-Tao Fakultät für Physik Universität Bielefeld Universitätsstraße 25 BielefeldD-33615 Germany Institut für Kernphysik Technische Universität Darmstadt Schloßgartenstraße 9 DarmstadtD-64289 Germany Paderborn Center for Parallel Computing Paderborn University Pohlweg 51 PaderbornD-33098 Germany Institut für Theoretische Physik Universität Regensburg Universitätsstraße 31 RegensburgD-93053 Germany

In a recently published work we employ gradient flow on the lattice to extract the leading contribution of the heavy quark momentum diffusion coefficient in the heavy quark limit from calculations of a well-known two-point function of color-electric field operators. In this article we want to report the progress of calculating the recently derived color-magnetic correlator that encodes a finite mass correction to this transport coefficient. The calculations we present here are based on the same ensemble of quenched gauge configurations at 1.5 Tc that we previously used for the color-electric correlator. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0)

关键词： Color

The virtual resource manager: an architecture for SLA-aware resource management 04

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The virtual resource manager: an architecture for SLA-aware ...

IEEE/ACM International Symposium on Cluster computing and the Grid (CCGRID)

作者： L.-O. Burchard M. Hovestadt O. Kao A. Keller B. Linnert Faculty of Computer Science and Electrical Engineering Technische Universität Berlin Germany Paderbom Center of Parallel Computing (PC2) Universitat Paderborn Germany

ISBN: (纸本)9780780384309

The next generation Grid will demand the Grid middleware to provide flexibility, transparency, and reliability. This implies the appliance of service level agreements to guarantee a negotiated level of quality of service. These requirements also affect the local resource management systems providing resources for the Grid. At this a gap between these demands and the features of today's resource management systems becomes apparent. In this paper we present an approach which closes this gap. Introducing the architecture of the virtual resource manager we highlight its main features of runtime responsibility, resource virtualization, information hiding, autonomy provision, and smooth integration of existing resource management system installations.

关键词： Resource management Computer architecture Middleware Grid computing Resource virtualization Quality of service Computer network management Computer science parallel processing Home appliances