Swiss National Supercomputing Center

Lugano, Switzerland

Swiss National Supercomputing Center

Lugano, Switzerland

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Jang Y.,ETH Zurich | Varetto U.,Swiss National Supercomputing Center
Acta Crystallographica Section A: Foundations of Crystallography | Year: 2010

Simulation and computation in chemistry studies have improved as computational power has increased over recent decades. Many types of chemistry simulation results are available, from atomic level bonding to volumetric representations of electron density. However, tools for the visualization of the results from quantum-chemistry computations are still limited to showing atomic bonds and isosurfaces or isocontours corresponding to certain isovalues. In this work, we study the volumetric representations of the results from quantum-chemistry computations, and evaluate and visualize the representations directly on a modern graphics processing unit without resampling the result in grid structures. Our visualization tool handles the direct evaluation of the approximated wavefunctions described as a combination of Gaussian-like primitive basis functions. For visualizations, we use a slice-based volume-rendering technique with a two-dimensional transfer function, volume clipping and illustrative rendering in order to reveal and enhance the quantum-chemistry structure. Since there is no need to resample the volume from the functional representations for the volume rendering, two issues, data transfer and resampling resolution, can be ignored; therefore, it is possible to explore interactively a large amount of different information in the computation results. © 2010 International Union of Crystallography Printed in Singapore - all rights reserved.


Jocksch A.,Swiss National Supercomputing Center
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2016

We present a diffusion process on graphs for k-way partitioning. In this approach, various species propagate on the graph that cancel each other out, and every partition is represented by one species of the converged solution. The vertices and edges of the graph are reservoirs and resistances, respectively, and source terms are placed on the vertices. A distribution of these source terms on the graph is suggested and the resulting k-way partitioning of the diffusion process for basic graphs discussed. We present reference examples in which complex graphs are recursively bi-partitioned with a diffusion step and a subsequent Kernighan-Lin improvement step. For comparison the graphs are also partitioned with multilevel methods and a subsequent Kernighan- Lin improvement. For certain graphs the diffusion approach produces the best partitions. © Springer International Publishing Switzerland 2016.


Lawson Daku L.M.,University of Geneva | Aquilante F.,Uppsala University | Robinson T.W.,Swiss National Supercomputing Center | Hauser A.,University of Geneva
Journal of Chemical Theory and Computation | Year: 2012

Highly accurate estimates of the high-spin/low-spin energy difference δEHL el in the high-spin complexes [Fe(NCH) 6] 2+ and [Co(NCH) 6] 2+ have been obtained from the results of CCSD(T) calculations extrapolated to the complete basis set limit. These estimates are shown to be strongly influenced by scalar relativistic effects. They have been used to assess the performances of the CASPT2 method and 30 density functionals of the GGA, meta-GGA, global hybrid, RSH, and double-hybrid types. For the CASPT2 method, the results of the assessment support the proposal [Kepenekian, M.; Robert, V.; Le Guennic, B. J. Chem. Phys. 2009, 131, 114702] that the ionization potential-electron affinity (IPEA) shift defining the zeroth-order Hamiltonian be raised from its standard value of 0.25 au to 0.50-0.70 au for the determination of δEHL el in Fe(II) complexes with a [FeN 6] core. At the DFT level, some of the assessed functionals proved to perform within chemical accuracy (±350 cm -1) for the spin-state energetics of [Fe(NCH) 6] 2+, others for that of [Co(NCH) 6] 2+, but none of them simultaneously for both complexes. As demonstrated through a reparametrization of the CAM-PBE0 range-separated hybrid, which led to a functional that performs within chemical accuracy for the spin-state energetics of both complexes, performing density functionals of broad applicability may be devised by including in their training sets highly accurate data like those reported here for [Fe(NCH) 6] 2+ and [Co(NCH) 6] 2+. © 2012 American Chemical Society.


Vazza F.,Jacobs University Bremen | Vazza F.,National institute for astrophysics | Bruggen M.,Jacobs University Bremen | Gheller C.,Swiss National Supercomputing Center
Monthly Notices of the Royal Astronomical Society | Year: 2013

We investigate the observable effects of feedback from active galactic nuclei (AGN) on nonthermal components of the intracluster medium (ICM). We have modelled feedback from AGN in cosmological simulations with the adaptive mesh refinement code ENZO, investigating three types of feedback that are sometimes called quasar, jet and radio mode. Using a small set of galaxy clusters simulated at high resolution, we model the injection and evolution of cosmic rays, as well as their effects on the thermal plasma. By comparing both the profiles of thermal gas to observed profiles from the ACCEPT sample and the secondary γ -ray emission to the available upper limits from Fermi, we discuss how the combined analysis of these two observables can constrain the energetics and mechanisms of feedback models in clusters. Those modes of AGN feedback that provide a good match to X-ray observations yield a γ -ray luminosity resulting from secondary cosmic rays that is about 10 times below the available upper limits from Fermi. Moreover, we investigate the injection of turbulent motions into the ICM from AGN, and the detectability of these motions via the analysis of line broadening of the Fe XXIII line. In the near future, deeper observations/upper limits of non-thermal emissions from galaxy clusters will yield stringent constraints on the energetics and modes of AGN feedback, even at early cosmic epochs. © 2012 The Authors.


News Article | March 11, 2016
Site: www.nanotech-now.com

Abstract: All materials are made up of atoms, which vibrate. These vibrations, or 'phonons', are responsible, for example, for how electric charge and heat is transported in materials. Vibrations of metals, semiconductors, and insulators in are well studied; however, now materials are being nanosized to bring better performance to applications such as displays, sensors, batteries, and catalytic membranes. What happens to vibrations when a material is nanosized has until now not been understood. Soft Surfaces Vibrate Strongly In a recent publication in Nature, ETH Professor Vanessa Wood and her colleagues explain what happens to atomic vibrations when materials are nanosized and how this knowledge can be used to systematically engineer nanomaterials for different applications. The paper shows that when materials are made smaller than about 10 to 20 nanometers -- that is, 5,000 times thinner than a human air -- the vibrations of the outermost atomic layers on surface of the nanoparticle are large and play an important role in how this material behaves. "For some applications, like catalysis, thermoelectrics, or superconductivity, these large vibrations may be good, but for other applications like LEDs or solar cells, these vibrations are undesirable," explains Wood. Indeed, the paper explains why nanoparticle-based solar cells have until now not met their full promise. The researchers showed using both experiment and theory that surface vibrations interact with electrons to reduce the photocurrent in solar cells. "Now that we have proven that surface vibrations are important, we can systematically design materials to suppress or enhance these vibrations," say Wood. Improving Solar Cells Wood's research group has worked for a long time on a particular type of nanomaterial -- colloidal nanocrystals -- semiconductors with a diameter of 2 to 10 nanometers. These materials are interesting because their optical and electrical properties are dependent on their size, which can be easily changed during their synthesis. These materials are now used commercially as red- and green-light emitters in LED-based TVs and are being explored as possible materials for low cost, solution-processed solar cells. Researchers have noticed that placing certain atoms around the surface of the nanocrystal can improve the performance of solar cells. The reason why this worked had not been understood. The work published in the Nature paper now gives the answer: a hard shell of atoms can suppress the vibrations and their interaction with electrons. This means a higher photocurrent and a higher efficiency solar cell. Big Science to Study the Nanoscale Experiments were conducted in Professor Wood's labs at ETH Zurich and at the Swiss Spallation Neutron Source at the Paul Scherrer Institute. By observing how neutrons scatter off atoms in a material, it is possible to quantify how atoms in a material vibrate. To understand the neutron measurements, simulations of the atomic vibrations were run at the Swiss National Supercomputing Center (CSCS) in Lugano. Wood says, "without access to these large facilities, this work would not have been possible. We are incredibly fortunate here in Switzerland to have these world class facilities." For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.


News Article | March 10, 2016
Site: www.cemag.us

All materials are made up of atoms, which vibrate. These vibrations, or "phonons", are responsible, for example, for how electric charge and heat is transported in materials. Vibrations of metals, semiconductors, and insulators in are well studied; however, now materials are being nanosized to bring better performance to applications such as displays, sensors, batteries, and catalytic membranes. What happens to vibrations when a material is nanosized has until now not been understood. In a recent publication in Nature, ETH Zürich Professor Vanessa Wood and her colleagues explain what happens to atomic vibrations when materials are nanosized and how this knowledge can be used to systematically engineer nanomaterials for different applications. The paper shows that when materials are made smaller than about 10 to 20 nanometers — that is, 5,000 times thinner than a human air — the vibrations of the outermost atomic layers on surface of the nanoparticle are large and play an important role in how this material behaves. “For some applications, like catalysis, thermoelectrics, or superconductivity, these large vibrations may be good, but for other applications like LEDs or solar cells, these vibrations are undesirable,” explains Wood. Indeed, the paper explains why nanoparticle-based solar cells have until now not met their full promise. The researchers showed using both experiment and theory that surface vibrations interact with electrons to reduce the photocurrent in solar cells. “Now that we have proven that surface vibrations are important, we can systematically design materials to suppress or enhance these vibrations,” says Wood. Wood’s research group has worked for a long time on a particular type of nanomaterial — colloidal nanocrystals — semiconductors with a diameter of 2 to 10 nanometers. These materials are interesting because their optical and electrical properties are dependent on their size, which can be easily changed during their synthesis. These materials are now used commercially as red- and green-light emitters in LED-based TVs and are being explored as possible materials for low cost, solution-processed solar cells. Researchers have noticed that placing certain atoms around the surface of the nanocrystal can improve the performance of solar cells. The reason why this worked had not been understood. The work published in the Nature paper now gives the answer: a hard shell of atoms can suppress the vibrations and their interaction with electrons. This means a higher photocurrent and a higher efficiency solar cell. Experiments were conducted in Wood’s labs at ETH Zurich and at the Swiss Spallation Neutron Source at the Paul Scherrer Institute. By observing how neutrons scatter off atoms in a material, it is possible to quantify how atoms in a material vibrate. To understand the neutron measurements, simulations of the atomic vibrations were run at the Swiss National Supercomputing Center (CSCS) in Lugano. Wood says, “without access to these large facilities, this work would not have been possible. We are incredibly fortunate here in Switzerland to have these world class facilities.”


News Article | March 9, 2016
Site: phys.org

Researchers at ETH have shown for the first time what happens to atomic vibrations when materials are nanosized and how this knowledge can be used to systematically engineer nanomaterials for different applications. Using both experiment, simulation, and theory, they explain how and why vibriations at the surface of a nanomaterial (q) can interact strongly with electrons (k and k'). Credit: Deniz Bozyigit / ETH Zurich All materials are made up of atoms, which vibrate. These vibrations, or 'phonons', are responsible, for example, for how electric charge and heat is transported in materials. Vibrations of metals, semiconductors, and insulators in are well studied; however, now materials are being nanosized to bring better performance to applications such as displays, sensors, batteries, and catalytic membranes. What happens to vibrations when a material is nanosized has until now not been understood. In a recent publication in Nature, ETH Professor Vanessa Wood and her colleagues explain what happens to atomic vibrations when materials are nanosized and how this knowledge can be used to systematically engineer nanomaterials for different applications. The paper shows that when materials are made smaller than about 10 to 20 nanometers—that is, 5,000 times thinner than a human air—the vibrations of the outermost atomic layers on surface of the nanoparticle are large and play an important role in how this material behaves. "For some applications, like catalysis, thermoelectrics, or superconductivity, these large vibrations may be good, but for other applications like LEDs or solar cells, these vibrations are undesirable," explains Wood. Indeed, the paper explains why nanoparticle-based solar cells have until now not met their full promise. The researchers showed using both experiment and theory that surface vibrations interact with electrons to reduce the photocurrent in solar cells. "Now that we have proven that surface vibrations are important, we can systematically design materials to suppress or enhance these vibrations," say Wood. Wood's research group has worked for a long time on a particular type of nanomaterial—colloidal nanocrystals—semiconductors with a diameter of 2 to 10 nanometers. These materials are interesting because their optical and electrical properties are dependent on their size, which can be easily changed during their synthesis. These materials are now used commercially as red- and green-light emitters in LED-based TVs and are being explored as possible materials for low cost, solution-processed solar cells. Researchers have noticed that placing certain atoms around the surface of the nanocrystal can improve the performance of solar cells. The reason why this worked had not been understood. The work published in the Nature paper now gives the answer: a hard shell of atoms can suppress the vibrations and their interaction with electrons. This means a higher photocurrent and a higher efficiency solar cell. Experiments were conducted in Professor Wood's labs at ETH Zurich and at the Swiss Spallation Neutron Source at the Paul Scherrer Institute. By observing how neutrons scatter off atoms in a material, it is possible to quantify how atoms in a material vibrate. To understand the neutron measurements, simulations of the atomic vibrations were run at the Swiss National Supercomputing Center (CSCS) in Lugano. Wood says, "without access to these large facilities, this work would not have been possible. We are incredibly fortunate here in Switzerland to have these world class facilities." More information: Deniz Bozyigit et al. Soft surfaces of nanomaterials enable strong phonon interactions, Nature (2016). DOI: 10.1038/nature16977


News Article | March 17, 2016
Site: www.materialstoday.com

Materials are made up of atoms that vibrate, and these vibrations, or 'phonons', are responsible for how electric charge and heat is transported in the materials. Atomic vibrations in metals, semiconductors and insulators are well studied, but what happens to atomic vibrations when a material is nanosized is far less well understood. In a recent paper in Nature, Vanessa Wood at ETH Zurich in Switzerland and her colleagues explain what happens to atomic vibrations when materials are nanosized and how this knowledge can be used to systematically engineer nanomaterials for different applications. Their paper shows that for nanomaterials smaller than about 10–20nm the vibrations of the outermost atomic layers at the surface of the nanomaterial are comparatively large and play an important role in how it behaves. "For some applications, like catalysis, thermoelectrics or superconductivity, these large vibrations may be good, but for other applications like LEDs or solar cells, these vibrations are undesirable," explains Wood. Indeed, the paper helps to explain why nanoparticle-based solar cells have until now not reached their full potential. The researchers showed using both experiment and theory that these surface vibrations interact with electrons to reduce the photocurrent in solar cells. "Now that we have proven that surface vibrations are important, we can systematically design materials to suppress or enhance these vibrations," says Wood. Wood's research group has worked for some time on a particular type of nanomaterial known as colloidal nanocrystals, which are semiconductors with a diameter of 2–10nm. These materials are interesting because their optical and electrical properties are dependent on their size, which can be easily changed during their synthesis. Colloidal nanocrystals are already being used commercially as emitters of red and green light in LED-based TVs and are also being explored as possible materials for low cost, solution-processed solar cells. Researchers have noticed that placing certain atoms around the surface of the nanocrystals can improve the performance of the solar cells, but the reason why this works has not been understood. The work published in the Nature paper now provides the answer: a hard shell of atoms can suppress the surface vibrations and their interaction with electrons, producing a higher photocurrent and a higher efficiency solar cell. The experiments were conducted in Wood's labs at ETH Zurich and at the Swiss Spallation Neutron Source at the Paul Scherrer Institute, also in Switzerland. By observing how neutrons scatter off atoms in a material, it is possible to quantify how the atoms in a material vibrate. To understand the neutron measurements, simulations of the atomic vibrations were run at the Swiss National Supercomputing Center in Lugano. "Without access to these large facilities, this work would not have been possible," says Wood. "We are incredibly fortunate here in Switzerland to have these world-class facilities." This story is adapted from material from ETH Zurich, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.


News Article | March 9, 2016
Site: www.rdmag.com

All materials are made up of atoms, which vibrate. These vibrations, or 'phonons', are responsible, for example, for how electric charge and heat is transported in materials. Vibrations of metals, semiconductors, and insulators in are well studied; however, now materials are being nanosized to bring better performance to applications such as displays, sensors, batteries, and catalytic membranes. What happens to vibrations when a material is nanosized has until now not been understood. In a recent publication in Nature, ETH Professor Vanessa Wood and her colleagues explain what happens to atomic vibrations when materials are nanosized and how this knowledge can be used to systematically engineer nanomaterials for different applications. The paper shows that when materials are made smaller than about 10 to 20 nanometers -- that is, 5,000 times thinner than a human air -- the vibrations of the outermost atomic layers on surface of the nanoparticle are large and play an important role in how this material behaves. "For some applications, like catalysis, thermoelectrics, or superconductivity, these large vibrations may be good, but for other applications like LEDs or solar cells, these vibrations are undesirable," explains Wood. Indeed, the paper explains why nanoparticle-based solar cells have until now not met their full promise. The researchers showed using both experiment and theory that surface vibrations interact with electrons to reduce the photocurrent in solar cells. "Now that we have proven that surface vibrations are important, we can systematically design materials to suppress or enhance these vibrations," say Wood. Wood's research group has worked for a long time on a particular type of nanomaterial -- colloidal nanocrystals -- semiconductors with a diameter of 2 to 10 nanometers. These materials are interesting because their optical and electrical properties are dependent on their size, which can be easily changed during their synthesis. These materials are now used commercially as red- and green-light emitters in LED-based TVs and are being explored as possible materials for low cost, solution-processed solar cells. Researchers have noticed that placing certain atoms around the surface of the nanocrystal can improve the performance of solar cells. The reason why this worked had not been understood. The work published in the Nature paper now gives the answer: a hard shell of atoms can suppress the vibrations and their interaction with electrons. This means a higher photocurrent and a higher efficiency solar cell. Experiments were conducted in Professor Wood's labs at ETH Zurich and at the Swiss Spallation Neutron Source at the Paul Scherrer Institute. By observing how neutrons scatter off atoms in a material, it is possible to quantify how atoms in a material vibrate. To understand the neutron measurements, simulations of the atomic vibrations were run at the Swiss National Supercomputing Center (CSCS) in Lugano. Wood said, "without access to these large facilities, this work would not have been possible. We are incredibly fortunate here in Switzerland to have these world class facilities."


News Article | November 10, 2016
Site: www.eurekalert.org

OAK RIDGE, Tenn., Nov. 10, 2016--Leaders in hybrid accelerated high-performance computing (HPC) in the United States (U.S.), Japan, and Switzerland have signed a memorandum of understanding (MOU) establishing an international institute dedicated to common goals, the sharing of HPC expertise, and forward-thinking evaluation of computing architecture. The MOU authorizes the creation of the Accelerated Data Analytics and Computing (ADAC) institute to support collaborative projects and programs that bridge the respective HPC missions of the U.S. Department of Energy's (DOE) Oak Ridge National Laboratory (ORNL), the Tokyo Institute of Technology (Tokyo Tech), and the Swiss Federal Institute of Technology, Zurich (ETH Zurich). All three organizations manage HPC centers that run large, GPU-accelerated supercomputers and provide key HPC capabilities to academia, government, and industry to solve many of the world's most complex and pressing scientific problems. "Forecasting the future of leadership-class computing and managing the risk of architectural change is a shared interest among ORNL, Tokyo Tech, and ETH Zurich," said Jeff Nichols, associate laboratory director of computing and computational sciences at ORNL. "What unites our three organizations is a willingness to embrace change, actively partner with HPC vendors, and devise solutions that advance the work of our scientific users. ADAC provides a framework for member organizations to pursue mutual interests such as accelerated node architectures as computing moves toward the exascale era and beyond." ADAC will focus on multiple objectives spanning performance, hardware, and applications, including: The institute lays the groundwork for more focused collaboration centered around three inaugural technical areas--applications, performance, and resource management. Designated representatives from each member institution serve as the leads in these areas. "ADAC is unique in that while all of these research centers compete on some level, the challenges we face are very similar. From application development to fully utilizing novel architectures, we can better evolve toward the exascale by sharing our problems and solutions," said Satoshi Matsuoka of the Global Scientific Information and Computing Center at Tokyo Tech, adding that the initial three-member collaboration could grow to include other institutions in the future. Thomas Schulthess, of the Swiss National Supercomputing Center (CSCS) at ETH Zurich, echoed Nichols' and Satoshi's sentiment: "ADAC is an acknowledgement that, despite the myriad accomplishments in accelerated computing, significant challenges remain. These challenges require collaboration across the HPC spectrum in order for our users to continue to push the frontiers of science, and, by extension, computing." Oak Ridge National Laboratory is home to the Oak Ridge Leadership Computing Facility, a DOE Office of Science User Facility. UT-Battelle manages ORNL for the DOE's Office of Science. The Office of Science is the single largest supporter of basic research in the physical sciences in the U.S., and is working to address some of the most pressing challenges of our time. For more information, please visit http://science. . Caption: ADAC members from ORNL, ETH Zurich and Tokyo Tech gathered in Lugano, Switzerland for a workshop earlier this year. NOTE TO EDITORS: You may read other press releases from Oak Ridge National Laboratory or learn more about the lab at http://www. . Additional information about ORNL is available at the sites below:

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