@article{17065, author = {{Esser, Norbert and Schmidt, Wolf Gero}}, issn = {{0370-1972}}, journal = {{physica status solidi (b)}}, number = {{256}}, title = {{{Electric Field Induced Raman Scattering at the Sb–InP(110) Interface: The Surface Dipole Contribution}}}, doi = {{10.1002/pssb.201800314}}, year = {{2018}}, } @article{18, abstract = {{Branch and bound (B&B) algorithms structure the search space as a tree and eliminate infeasible solutions early by pruning subtrees that cannot lead to a valid or optimal solution. Custom hardware designs significantly accelerate the execution of these algorithms. In this article, we demonstrate a high-performance B&B implementation on FPGAs. First, we identify general elements of B&B algorithms and describe their implementation as a finite state machine. Then, we introduce workers that autonomously cooperate using work stealing to allow parallel execution and full utilization of the target FPGA. Finally, we explore advantages of instance-specific designs that target a specific problem instance to improve performance. We evaluate our concepts by applying them to a branch and bound problem, the reconstruction of corrupted AES keys obtained from cold-boot attacks. The evaluation shows that our work stealing approach is scalable with the available resources and provides speedups proportional to the number of workers. Instance-specific designs allow us to achieve an overall speedup of 47 × compared to the fastest implementation of AES key reconstruction so far. Finally, we demonstrate how instance-specific designs can be generated just-in-time such that the provided speedups outweigh the additional time required for design synthesis.}}, author = {{Riebler, Heinrich and Lass, Michael and Mittendorf, Robert and Löcke, Thomas and Plessl, Christian}}, issn = {{1936-7406}}, journal = {{ACM Transactions on Reconfigurable Technology and Systems (TRETS)}}, keywords = {{coldboot}}, number = {{3}}, pages = {{24:1--24:23}}, publisher = {{Association for Computing Machinery (ACM)}}, title = {{{Efficient Branch and Bound on FPGAs Using Work Stealing and Instance-Specific Designs}}}, doi = {{10.1145/3053687}}, volume = {{10}}, year = {{2017}}, } @inproceedings{1592, abstract = {{Compared to classical HDL designs, generating FPGA with high-level synthesis from an OpenCL specification promises easier exploration of different design alternatives and, through ready-to-use infrastructure and common abstractions for host and memory interfaces, easier portability between different FPGA families. In this work, we evaluate the extent of this promise. To this end, we present a parameterized FDTD implementation for photonic microcavity simulations. Our design can trade-off different forms of parallelism and works for two independent OpenCL-based FPGA design flows. Hence, we can target FPGAs from different vendors and different FPGA families. We describe how we used pre-processor macros to achieve this flexibility and to work around different shortcomings of the current tools. Choosing the right design configurations, we are able to present two extremely competitive solutions for very different FPGA targets, reaching up to 172 GFLOPS sustained performance. With the portability and flexibility demonstrated, code developers not only avoid vendor lock-in, but can even make best use of real trade-offs between different architectures.}}, author = {{Kenter, Tobias and Förstner, Jens and Plessl, Christian}}, booktitle = {{Proc. Int. Conf. on Field Programmable Logic and Applications (FPL)}}, keywords = {{tet_topic_hpc}}, publisher = {{IEEE}}, title = {{{Flexible FPGA design for FDTD using OpenCL}}}, doi = {{10.23919/FPL.2017.8056844}}, year = {{2017}}, } @article{1589, author = {{Schumacher, Jörn and Plessl, Christian and Vandelli, Wainer}}, journal = {{Journal of Physics: Conference Series}}, publisher = {{IOP Publishing}}, title = {{{High-Throughput and Low-Latency Network Communication with NetIO}}}, doi = {{10.1088/1742-6596/898/8/082003}}, volume = {{898}}, year = {{2017}}, } @article{10023, abstract = {{We perform a comprehensive theoretical study of the structural and electronic properties of potassium niobate (KNbO3) in the cubic, tetragonal, orthorhombic, monoclinic, and rhombohedral phase, based on density-functional theory. The influence of different parametrizations of the exchange-correlation functional on the investigated properties is analyzed in detail, and the results are compared to available experimental data. We argue that the PBEsol and AM05 generalized gradient approximations as well as the RTPSS meta-generalized gradient approximation yield consistently accurate structural data for both the external and internal degrees of freedom and are overall superior to the local-density approximation or other conventional generalized gradient approximations for the structural characterization of KNbO3. Band-structure calculations using a HSE-type hybrid functional further indicate significant near degeneracies of band-edge states in all phases which are expected to be relevant for the optical response of the material.}}, author = {{Schmidt, Falko and Landmann, Marc and Rauls, Eva and Argiolas, Nicola and Sanna, Simone and Schmidt, Wolf Gero and Schindlmayr, Arno}}, issn = {{1687-8442}}, journal = {{Advances in Materials Science and Engineering}}, publisher = {{Hindawi}}, title = {{{Consistent atomic geometries and electronic structure of five phases of potassium niobate from density-functional theory}}}, doi = {{10.1155/2017/3981317}}, volume = {{2017}}, year = {{2017}}, } @article{13353, author = {{Lewandowski, Przemyslaw and Luk, Samuel M. H. and Chan, Chris K. P. and Leung, P. T. and Kwong, N. H. and Binder, Rolf and Schumacher, Stefan}}, issn = {{1094-4087}}, journal = {{Optics Express}}, number = {{25}}, title = {{{Directional optical switching and transistor functionality using optical parametric oscillation in a spinor polariton fluid}}}, doi = {{10.1364/oe.25.031056}}, volume = {{25}}, year = {{2017}}, } @article{13354, author = {{Luk, S. M. H. and Kwong, N. H. and Lewandowski, P. and Schumacher, Stefan and Binder, R.}}, issn = {{0031-9007}}, journal = {{Physical Review Letters}}, number = {{11}}, title = {{{Optically Controlled Orbital Angular Momentum Generation in a Polaritonic Quantum Fluid}}}, doi = {{10.1103/physrevlett.119.113903}}, volume = {{119}}, year = {{2017}}, } @article{13364, author = {{Kwong, N H and Tsang, C Y and Luk, Samuel M H and Tse, Y C and Chan, Chris K P and Lewandowski, P and Leung, P T and Schumacher, Stefan and Binder, R}}, issn = {{0031-8949}}, journal = {{Physica Scripta}}, title = {{{Optical switching of polariton density patterns in a semiconductor microcavity}}}, doi = {{10.1088/1402-4896/aa58f6}}, year = {{2017}}, } @article{13360, author = {{Wiebeler, Christian and Plasser, Felix and Hedley, Gordon J. and Ruseckas, Arvydas and Samuel, Ifor D. W. and Schumacher, Stefan}}, issn = {{1948-7185}}, journal = {{The Journal of Physical Chemistry Letters}}, pages = {{1086--1092}}, title = {{{Ultrafast Electronic Energy Transfer in an Orthogonal Molecular Dyad}}}, doi = {{10.1021/acs.jpclett.7b00089}}, year = {{2017}}, } @article{10021, abstract = {{The optical properties of pristine and titanium-doped LiNbO3 are modeled from first principles. The dielectric functions are calculated within time-dependent density-functional theory, and a model long-range contribution is employed for the exchange-correlation kernel in order to account for the electron-hole binding. Our study focuses on the influence of substitutional titanium atoms on lithium sites. We show that an increasing titanium concentration enhances the values of the refractive indices and the reflectivity.}}, author = {{Friedrich, Michael and Schmidt, Wolf Gero and Schindlmayr, Arno and Sanna, Simone}}, issn = {{2475-9953}}, journal = {{Physical Review Materials}}, number = {{3}}, publisher = {{American Physical Society}}, title = {{{Optical properties of titanium-doped lithium niobate from time-dependent density-functional theory}}}, doi = {{10.1103/PhysRevMaterials.1.034401}}, volume = {{1}}, year = {{2017}}, } @article{13424, author = {{Aldahhak, Hazem and Paszkiewicz, M. and Allegretti, F. and Duncan, D. A. and Tebi, S. and Deimel, P. S. and Casado Aguilar, P. and Zhang, Y.-Q. and Papageorgiou, A. C. and Koch, R. and Barth, J. V. and Schmidt, Wolf Gero and Müllegger, S. and Schöfberger, W. and Klappenberger, F. and Rauls, E. and Gerstmann, Uwe}}, issn = {{1932-7447}}, journal = {{The Journal of Physical Chemistry C}}, pages = {{2192--2200}}, title = {{{X-ray Spectroscopy of Thin Film Free-Base Corroles: A Combined Theoretical and Experimental Characterization}}}, doi = {{10.1021/acs.jpcc.6b09935}}, volume = {{121}}, year = {{2017}}, } @article{13423, author = {{Tebi, Stefano and Paszkiewicz, Mateusz and Aldahhak, Hazem and Allegretti, Francesco and Gonglach, Sabrina and Haas, Michael and Waser, Mario and Deimel, Peter S. and Aguilar, Pablo Casado and Zhang, Yi-Qi and Papageorgiou, Anthoula C. and Duncan, David A. and Barth, Johannes V. and Schmidt, Wolf Gero and Koch, Reinhold and Gerstmann, Uwe and Rauls, Eva and Klappenberger, Florian and Schöfberger, Wolfgang and Müllegger, Stefan}}, issn = {{1936-0851}}, journal = {{ACS Nano}}, pages = {{3383--3391}}, title = {{{On-Surface Site-Selective Cyclization of Corrole Radicals}}}, doi = {{10.1021/acsnano.7b00766}}, year = {{2017}}, } @article{13426, author = {{Edler, F. and Miccoli, I. and Stöckmann, J. P. and Pfnür, H. and Braun, Christian and Neufeld, Sergej and Sanna, S. and Schmidt, Wolf Gero and Tegenkamp, C.}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{12}}, title = {{{Tuning the conductivity along atomic chains by selective chemisorption}}}, doi = {{10.1103/physrevb.95.125409}}, volume = {{95}}, year = {{2017}}, } @article{13427, author = {{Nozaki, Daijiro and Lücke, Andreas and Schmidt, Wolf Gero}}, issn = {{1948-7185}}, journal = {{The Journal of Physical Chemistry Letters}}, pages = {{727--732}}, title = {{{Molecular Orbital Rule for Quantum Interference in Weakly Coupled Dimers: Low-Energy Giant Conductivity Switching Induced by Orbital Level Crossing}}}, doi = {{10.1021/acs.jpclett.6b02989}}, year = {{2017}}, } @article{13425, author = {{Rohrmüller, M. and Schmidt, Wolf Gero and Gerstmann, Uwe}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{12}}, title = {{{Electron paramagnetic resonance calculations for hydrogenated Si surfaces}}}, doi = {{10.1103/physrevb.95.125310}}, volume = {{95}}, year = {{2017}}, } @article{13416, abstract = {{The optical properties of congruent lithium niobate are analyzed from first principles. The dielectric function of the material is calculated within time-dependent density-functional theory. The effects of isolated intrinsic defects and defect pairs, including the NbLi4+ antisite and the NbLi4+−NbNb4+ pair, commonly addressed as a bound polaron and bipolaron, respectively, are discussed in detail. In addition, we present further possible realizations of polaronic and bipolaronic systems. The absorption feature around 1.64 eV, ascribed to small bound polarons [O. F. Schirmer et al., J. Phys.: Condens. Matter 21, 123201 (2009)], is nicely reproduced within these models. Among the investigated defects, we find that the presence of bipolarons at bound interstitial-vacancy pairs NbV−VLi can best explain the experimentally observed broad absorption band at 2.5 eV. Our results provide a microscopic model for the observed optical spectra and suggest that, besides NbLi antisites and Nb and Li vacancies, Nb interstitials are also formed in congruent lithium-niobate samples.}}, author = {{Friedrich, Michael and Schmidt, Wolf Gero and Schindlmayr, Arno and Sanna, Simone}}, issn = {{2475-9953}}, journal = {{Physical Review Materials}}, number = {{5}}, publisher = {{American Physical Society}}, title = {{{Polaron optical absorption in congruent lithium niobate from time-dependent density-functional theory}}}, doi = {{10.1103/PhysRevMaterials.1.054406}}, volume = {{1}}, year = {{2017}}, } @article{13419, author = {{Frigge, T. and Hafke, B. and Witte, T. and Krenzer, B. and Streubühr, C. and Samad Syed, A. and Mikšić Trontl, V. and Avigo, I. and Zhou, P. and Ligges, M. and von der Linde, D. and Bovensiepen, U. and Horn-von Hoegen, M. and Wippermann, S. and Lücke, A. and Sanna, S. and Gerstmann, Uwe and Schmidt, Wolf Gero}}, issn = {{0028-0836}}, journal = {{Nature}}, pages = {{207--211}}, title = {{{Optically excited structural transition in atomic wires on surfaces at the quantum limit}}}, doi = {{10.1038/nature21432}}, volume = {{544}}, year = {{2017}}, } @article{13421, author = {{Landmann, M. and Rauls, E. and Schmidt, Wolf Gero}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{15}}, title = {{{Understanding band alignments in semiconductor heterostructures: Composition dependence and type-I–type-II transition of natural band offsets in nonpolar zinc-blendeAlxGa1−xN/AlyGa1−yNcomposites}}}, doi = {{10.1103/physrevb.95.155310}}, volume = {{95}}, year = {{2017}}, } @article{13415, author = {{Braun, Christian and Hogan, Conor and Chandola, Sandhya and Esser, Norbert and Sanna, Simone and Schmidt, Wolf Gero}}, issn = {{2475-9953}}, journal = {{Physical Review Materials}}, number = {{5}}, title = {{{Si(775)-Au atomic chains: Geometry, optical properties, and spin order}}}, doi = {{10.1103/physrevmaterials.1.055002}}, volume = {{1}}, year = {{2017}}, } @article{13422, author = {{Witte, Matthias and Rohrmüller, Martin and Gerstmann, Uwe and Henkel, Gerald and Schmidt, Wolf Gero and Herres-Pawlis, Sonja}}, issn = {{0192-8651}}, journal = {{Journal of Computational Chemistry}}, pages = {{1752--1761}}, title = {{{[Cu6(NGuaS)6]2+ and its oxidized and reduced derivatives: Confining electrons on a torus}}}, doi = {{10.1002/jcc.24798}}, year = {{2017}}, }