| MAT-01 |
A Hybrid OpenMP/MPI Solver for First-principles Plane Wave Materials Science Codes, Andrew Canning (Lawrence Berkeley National Laboratory, USA) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
MAT-01
A Hybrid OpenMP/MPI Solver for First-principles Plane Wave Materials Science Codes, Andrew Canning (Lawrence Berkeley National Laboratory, USA)
Co-authors:
First-principles materials science codes based on density functional theory (DFT) and using plane waves (PW) have become the largest user (by method) of computer cycles at scientific computer centers around the world. We present a hybrid OpenMP/MPI Conjugate Gradient based iterative eigensolver that allows this approach to scale to tens of thousands of cores on modern many core parallel computers. Performance results will be presented for the Cray XE6 and XC30 architectures.
| MAT-02 |
A Solver for the Generalized Poisson Equation in Wet-environments Electronic-structure Calculations, Giuseppe Fisicaro (University of Basel, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
MAT-02
A Solver for the Generalized Poisson Equation in Wet-environments Electronic-structure Calculations, Giuseppe Fisicaro (University of Basel, Switzerland)
Co-authors: L. Genovese (CEA, France); S. Goedecker (University of Basel, Switzerland)
The computational study of chemical reactions in complex wet environments is critical for applications in many fields. In the present work we propose an algorithm, based on the Preconditioned Conjugate Gradient (PCG) method, to handle the Generalized Poisson equation. It allows to solve iteratively the minimization problem with some ten iterations. The algorithm takes advantage of a preconditioning procedure based on the BigDFT Poisson solver for the standard Poisson equation. It exhibits very high accuracy and parallel efficiency for different Boundary conditions. The solver has been integrated to the BigDFT main electronic-structure package and it will be released as a independent program.
| MAT-03 |
A Spherical P-method for Full-potential Electronic Structure Problems, Lukas Drescher (Technische Universität Berlin, Germany) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
MAT-03
A Spherical P-method for Full-potential Electronic Structure Problems, Lukas Drescher (Technische Universität Berlin, Germany)
Co-authors: Reinhold Schneider (Technische Universität Berlin, Germany); Kersten Schmidt (Technische Universität Berlin, Germany)
A major challenge in full-potential electronic structure calculations stems from singularities due to the nuclear Coulomb potential. An hp-adaptive FEM was recently shown to yield exponential convergence at the cost of a large number of degrees of freedom (NDOF) that accumulate at the nuclei. In this work, we propose a spherical discretization near the nuclei that is adapted to the core singularity. By coupling this approach to a FEM on the complementary domain in the mortar element framework, we obtain a pure p-method that reduces the NDOF at the nuclei substantially. The associated efficiency gain versus hp-FEM is shown on a numerical example from molecular Kohn-Sham DFT.
| MAT-04 |
Accelerating Nano-device Simulations with Extreme-scale Algorithms and Software Co-integration, Mathieu Luisier (ETH Zurich, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
MAT-04
Accelerating Nano-device Simulations with Extreme-scale Algorithms and Software Co-integration, Mathieu Luisier (ETH Zurich, Switzerland)
Co-authors: Nicola Marzari (EPFL, Switzerland); Olaf Schenk (Università della Svizzera italiana, Switzerland)
The ANSWERS project (Accelerating nano-device simulations with extreme-scale algorithms and software co-integration) is currently supported by the Platform for Advanced Scientific Computing (PASC). Its main objectives consist in developing numerical algorithms and software on hybrid manycore architectures specifically dedicated to ab-initio electronic structure and quantum transport calculations of realistic nanostructures. This poster intends to summarize the progresses of the project and highlight the future research directions.
| MAT-05 |
Achieving Linear Scaling in Computational Cost for a Fully Polarizable MM/Continuum Embedding, Louis Lagardère (UPMC, France) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
MAT-05
Achieving Linear Scaling in Computational Cost for a Fully Polarizable MM/Continuum Embedding, Louis Lagardère (UPMC, France)
Co-authors: Stefano Caprasecca (Università di Pisa, Italy); Sandro Jurinovich (Università di Pisa, Italy); Benjamin Stamm (Pierre-and-Marie-Curie University, France); Filippo Lipparini (Pierre-and-Marie-Curie University, France)
We present a new, efficient implementation of a fully polarizable QM/MM/continuum model based on an induced-dipoles polarizable force field and on the Conductor-like Screening Model as a polarizable continuum in combination with a self-consistent field QM method. A linear scaling with respect to both the computational cost and the memory requirements is achieved thanks to the use of the recently developed ddCOSMO model for the continuum and the Fast Multipole Method for the force field, together with an efficient iterative procedure. Therefore, it becomes possible to include in the classical layer as much as several tens of thousands of atoms with a limited computational effort.
| MAT-06 |
Computer Simulation and Neutron Scattering Investigations of Phospholipid Bilayers in Water Solutions of Room-Temperature Ionic Liquids, Antonio Benedetto (Paul Scherrer Institut, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
MAT-06
Computer Simulation and Neutron Scattering Investigations of Phospholipid Bilayers in Water Solutions of Room-Temperature Ionic Liquids, Antonio Benedetto (Paul Scherrer Institut, Switzerland)
Co-authors: Pietro Ballone (Università di Roma La Sapienza, Italy)
The recent development of the so-called ionic liquid (IL) family has expanded the number of ionic systems that could be used to affect the behaviour of biosystems through the properties of their interfacial water. Our study concerns the microscopic mechanisms underlying these effects, and relies on the combination of neutron scattering and molecular dynamics (MD) simulations. We present the results for the interaction of imidazolium-based ILs with phospholipid bilayers [JPhysChemB 2014, 118, 12192]. Neutron scattering and MD simulations (i) confirm the tendency of cations to be absorbed into the lipid phase, enhancing the penetration of water that (ii) apparent changes its relaxation time.
| MAT-07 |
DBCSR: Accelerated Sparse Matrix Multiplication Library, Andreas Glöss (ETH Zurich, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
MAT-07
DBCSR: Accelerated Sparse Matrix Multiplication Library, Andreas Glöss (ETH Zurich, Switzerland)
Co-authors: Alfio Lazzaro (ETH Zurich, Switzerland); Hans Pabst (Intel Semiconductor AG, Switzerland); Ole Schütt (ETH Zurich, Switzerland); Peter Messmer (NVIDIA, Switzerland); Joost VandeVondele (ETH Zurich, Switzerland); Jürg Hutter (University of Zurich, Switzerland)
DBCSR is a sparse matrix storage, manipulation and multiplication library. It is used in the CP2K quantum chemistry program and its multi-layered structure automatically takes care of and optimizes several computational aspects like parallelism (MPI, OMP, Accelerators), data (cache) locality and on-the-fly filtering. Here we describe the challenges and our solutions for designing the DBCSR library with a special focus on the backend layer and the backends (CPU, CUDA, OpenCL and MIC). The latter, as key components for accessing all available computational resources on a modern multicore hybrid system concurrently, will be explained in more detail.
| MAT-08 |
Developing Experimental & Theoretical Crystallography Open Databases, Andrius Merkys (EPFL, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
MAT-08
Developing Experimental & Theoretical Crystallography Open Databases, Andrius Merkys (EPFL, Switzerland)
Co-authors: Giovanni Pizzi (EPFL, Switzerland); Andrea Cepellotti (EPFL, Switzerland); Nicolas Mounet (EPFL, Switzerland); Saulius Grazulis (Vilnius University, Lithuania); Nicola Marzari (EPFL, Switzerland)
The Crystallography Open Database (COD), launched as a grass-root initiative by an international group of scientists, has become the largest open-access resource to date for experimentally determined small-molecule crystal structures and is ready to be used as a source for large-scale automated analyses in various fields of computational chemistry, such as drug design and material research. A variety of data access and selection options, cross-links with other resources are made possible thanks to the open-access nature of the COD. Recently, a similar effort - the Theoretical COD - was launched alongside the COD, aimed to collect the results of atomistic simulations in an unified format.
| MAT-09 |
DFT+DMFT Study of Strain and Interface Effects in D1 and D2 T2g-Perovskites, Gabriele Sclauzero (ETH Zurich, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
MAT-09
DFT+DMFT Study of Strain and Interface Effects in D1 and D2 T2g-Perovskites, Gabriele Sclauzero (ETH Zurich, Switzerland)
Co-authors: Krzysztof Dymkowski (ETH Zurich, Switzerland); Claude Ederer (ETH Zurich, Switzerland)
We address the metal-insulator transitions in epitaxial films of early-transition metal oxides through DFT+DMFT. We show that the Mott insulating phase in LaVO3 is robust against epitaxial strain, while LaTiO3 becomes metallic under compressive strains, in agreement with thin-film experiments. The combined effect of strain-induced changes in the crystal field splitting of t2g orbitals and the different t2g occupations of the two materials can account for this behaviour. The origin of the metallicity at the LaVO3/SrTiO3 interface is still unclear and calls for an explicit modelling of reconstruction effects at the thin-film/substrate interface.
| MAT-10 |
Direct Path Integral Estimators for Isotope Fractionation Ratios, Bingqing Cheng (EPFL, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
MAT-10
Direct Path Integral Estimators for Isotope Fractionation Ratios, Bingqing Cheng (EPFL, Switzerland)
Co-authors: Michele Ceriotti (EPFL, Switzerland);
We demonstrate that it is possible to evaluate the isotope fractionation ratios directly from path-integral molecular dynamics simulations. The corresponding estimators are derived from the ratio of the partition functions of the isotope substituted systems, which is obtained by a virtual substitution of the isotopes of
the tagged atom. Since it avoids the mass integration altogether it is more convenient, computationally advantageous, and immune to errors in the integral for the isotope mass. Finally, we demonstrate the efficiency of these estimators by applying them to investigate the isotope fractionation ratios in the gas-phase Zundel cation, and in a few simple hydrocarbons.
| MAT-11 |
EXAFS Spectra Interpretation Using Molecular Dynamics and DFT Simulations, Dmitry Bocharov (Paul Scherrer Institut, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
MAT-11
EXAFS Spectra Interpretation Using Molecular Dynamics and DFT Simulations, Dmitry Bocharov (Paul Scherrer Institut, Switzerland)
Co-authors: Matthias Krack (Paul Scherrer Institut, Switzerland); Alexei Kuzmin (University of Latvia, Latvia)
Extended X-Ray Absorption Fine Structure EXAFS spectroscopy is a powerful tool to study the local atomic structure of materials. The interpretation of the EXAFS spectra is a non-trivial task which is addressed in our study using two approaches, combining ab initio EXAFS theory with molecular dynamics simulations or first-principles electronic structure calculations. The atomic scale simulations were performed by the CP2K code for two systems: (i) pure and Cr-doped UO2 which are employed as nuclear fuel and (ii) pure ScF3 which attracted attention due to its negative thermal expansion over a wide range of temperatures. The advantages and limitations of both approaches are discussed.
| MAT-12 |
Large Scale Density Matrix Renormalization Group Calculations, Michele Dolfi (ETH Zurich, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
MAT-12
Large Scale Density Matrix Renormalization Group Calculations, Michele Dolfi (ETH Zurich, Switzerland)
Co-authors: Adrian Kantian (KTH Royal Institute of Technology / Stockholm University, Sweden); Alexandr Kosenkov (ETH Zurich, Switzerland); Bela Bauer (Microsoft Research, USA); Thierry Giamarchi (University of Geneva, Switzerland); Matthias Troyer (ETH Zurich, Switzerland)
The Density Matrix Renormalization Group (DMRG) is a very efficient method to study one-dimensional quantum systems. In higher dimensions, particularly in 2d, this technique requires to operate on matrices with a bond dimension 'm' scaling exponentially in the system width. We present the techniques used in our massively parallel DMRG application which allow the study of challenging systems up to m=30'000. Our test cases is the Hubbard models in weakly coupled chains and ladders. We apply the DMRG to this models to investigate theoretical models for superconductivity in cuprate materials and organic super conductors by studying the pairing correlations.
| MAT-13 |
Local Density Fitting within a Gaussian and Plane Waves Approach, Dorothea Golze (University of Zurich, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
MAT-13
Local Density Fitting within a Gaussian and Plane Waves Approach, Dorothea Golze (University of Zurich, Switzerland)
Co-authors: Marcella Iannuzzi (University of Zurich, Switzerland); Jürg Hutter (University of Zurich, Switzerland)
A local density fitting technique (LRI) is introduced for Kohn-Sham (KS) density functional theory calculations using a mixed Gaussian and plane waves (GPW) approach within the CP2K program package. In LRI, the atomic pair densities are approximated by an expansion in one-center fit functions reducing the prefactor for building the KS matrix. Furthermore, the scalability of the grid-based terms with respect to number of CPUs can be simplified and improved. Results are presented for liquid water demonstrating that the SCF step can be sped up by a factor of at least three for large and medium-sized systems. Reaction energies obtained by LRI prove that the approach is also accurate.
| MAT-14 |
New Spectroscopic Approaches for Periodic Systems, Sandra Luber (University of Zurich, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
MAT-14
New Spectroscopic Approaches for Periodic Systems, Sandra Luber (University of Zurich, Switzerland)
Co-authors: Jürg Hutter (University of Zurich, Switzerland)
Knowledge about local properties is extremely helpful for the analysis of structures and interactions. Calculations provide additional insight allowing, for instance, to quantify the contributions of solute and solvent molecules [1] or adsorbates on solids. We present novel, computationally efficient methods for the calculation of properties for periodic systems such as liquids and solids. These are applied to calculate, among others, vibrational spectra via ab initio molecular dynamics [2,3].
References:
[1] S. Luber, J. Phys. Chem. A, 117 2760 (2013).
[2] S. Luber, M. Iannuzzi, J. Hutter, J. Chem. Phys. 141 094503 (2014).
[3] S. Luber, J. Chem. Phys. 141 234110 (2014).
| MAT-15 |
Pyrphyrin Adsorption on Reconstructed and Ideal Au(111) Surface, Yeliz Gurdal (University of Zurich, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
MAT-15
Pyrphyrin Adsorption on Reconstructed and Ideal Au(111) Surface, Yeliz Gurdal (University of Zurich, Switzerland)
Co-authors: Marcella Iannuzzi (University of Zurich, Switzerland); Sandra Luber (University of Zurich, Switzerland); Jürg Hutter (University of Zurich, Switzerland)
We study adsorption of Pyrphyrin on ideal and reconstructed Au(111) surfaces and compare favorable adsorption geometries of the molecule by DFT simulations. The most stable adsorption state is the one with adsorption of CN links along Au axis. The interaction to the surface is dominated by van der Waals, but the orientation and deformation of the molecule are determined by the attraction between the CN groups and the closest Au atoms. Adsorption geometries of both monomer and dimer show differences with respect to the modeled Au surface. We will investigate the electronic structure of Pyrphyrin/Au by calculating molecular energy states, N1s XPS Spectra and STM images.
| MAT-16 |
Recognizing Molecular Patterns by Machine Learning: An Agnostic Structural Definition of the Hydrogen Bond, Piero Gasparotto (EPFL, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
MAT-16
Recognizing Molecular Patterns by Machine Learning: An Agnostic Structural Definition of the Hydrogen Bond, Piero Gasparotto (EPFL, Switzerland)
Co-authors: Michele Ceriotti (EPFL, Switzerland)
Atomistic simulations are getting increasingly more accurate, and make it possible to model predictively increasingly complex problems. In order to rationalize their behavior, a very promising approach is the use of machine-learning techniques (e.g. pattern recognition and dimensionality reduction) to provide a fully automated framework to understand structural patterns and to accelerate the exploration of the complex conformational landscape in a simulation. Here we demonstrate the use of a Probabilistic Analysis of Molecular Motifs (PAMM) method to provide an agnostic definition of the hydrogen bond, and discuss its application to the description of ab initio water models.
| MAT-17 |
Self-Assembly of Water-Methanol Mixtures at the Surface of Graphite, Daniele Giofrè (EPFL, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
MAT-17
Self-Assembly of Water-Methanol Mixtures at the Surface of Graphite, Daniele Giofrè (EPFL, Switzerland)
Co-authors: Michele Ceriotti (EPFL, Switzerland)
AFM experiments observed the formation of regular, striped patterns at the interface between a methanol/water solution and a graphite surface. The time scale for the formation of these patterns is beyond direct observation by atomistic simulations. Nevertheless, molecular dynamics shows segregation of methanol at the interface, and a high degree of topological and geometric order in the H-bond network. The regular pattern can then be explained as a regular array of defects originating due to the small mismatch between the periodicity of the substrate and the characteristic length-scale of the H-bond patterns.
| MAT-18 |
Solvation Effects on Electronic Energy Differences of a Co-Cubane, Florian Hodel (University of Zurich, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
MAT-18
Solvation Effects on Electronic Energy Differences of a Co-Cubane, Florian Hodel (University of Zurich, Switzerland)
Co-authors: Sandra Luber (University of Zurich, Switzerland); Juerg Hutter (University of Zurich, Switzerland)
We investigated the influence of different methods on electronic energy differences of ligand exchange reactions of a Co(II)-cubane based water oxidation catalyst. We compared average electronic energy differences obtained from sampling with born-Oppenheimer molecular dynamics using Kohn-Sham density functional theory to electronic energy differences of geometry optimized structures. In doing so, we also compared different levels of solvation ranging from hundreds of water molecules, first solvation shell, implicit solvent to in vacuo calculations, and finally also investigated barriers and free energies using the nudged elastic band method and metadynamics.
| MAT-19 |
The Computational Design of Pb Free and Stable Hybrid Materials for Solar Cells, Fadwa El Mellouhi (Qatar Environment and Energy Research Institute, Qatar) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
MAT-19
The Computational Design of Pb Free and Stable Hybrid Materials for Solar Cells, Fadwa El Mellouhi (Qatar Environment and Energy Research Institute, Qatar)
Co-authors: Fadwa El Mellouhi (Qatar Foundation, Qatar); Akinlolu Akande (Trinity College Dublin, Ireland); Sergey Rashkeev (Qatar Foundation, Qatar); Carlo Motta (Trinity College Dublin, Ireland); Stefano Sanvito (Trinity College Dublin, Ireland); Sabre Kais (Qatar Foundation, Qatar); Fahhad Alharbi (Qatar Foundation, Qatar)
In the past four years, the solar cell field has experienced an unprecedented meteoritic emergence of a new family of solar cell technologies; namely, perovskites solar cells (PSC) using (CH3NH3)PbI3 as absorber. However, two main challenges prevent deploying PSC technology: the presence of the toxic element lead (Pb) and their structural instability. Our efforts to design lead free family of hybrid materials demonstrate that the design of hybrid materials containing organic cations might require careful considerations among them the size of the cell used during the screening process. Our strategy will be presented as well as some resulting promising compounds.
| MAT-20 |
Towards an Ab Initio Electronic Transport Model for Photovoltaic Materials Design, Cynthia Lo (Washington University in St. Louis, United States) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
MAT-20
Towards an Ab Initio Electronic Transport Model for Photovoltaic Materials Design, Cynthia Lo (Washington University in St. Louis, United States)
Co-authors: Alireza Faghaninia (Washington University in St. Louis, USA); Maria Stoica (Washington University in St. Louis, USA)
Improvements in computational models of electronic transport are necessary for accurate predictions of photovoltaic behavior. Existing efforts to solve the Boltzmann transport equation employ approximations that result in incorrect trends in the calculated properties. Instead, we propose an ab initio model that explicitly determines elastic and inelastic scattering rates and charge carrier mobility. We have validated the calculated mobility of GaAs and InN, as a function of temperature and carrier concentration, against experimental data. We now show how this model is being used to screen new transparent conducting materials for low-cost photovoltaics.
| MAT-21 |
Understanding Enantioselectivity of PdGa High-Symmetry Surfaces, Aliaksandr Yakutovich (EMPA, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
MAT-21
Understanding Enantioselectivity of PdGa High-Symmetry Surfaces, Aliaksandr Yakutovich (EMPA, Switzerland)
Co-authors: Carlo A. Pignedoli (EMPA, Switzerland); Jan Prinz (EMPA, Switzerland); Roland Widmer (EMPA, Switzerland); Oliver Groening (EMPA, Switzerland); Daniele Passerone (EMPA, Switzerland)
The PdGa intermetallic compound emerged recently for its remarkable catalytic properties in the purification of the feedstock for polyethylene production. PdGa has an intrinsically chiral structure and can be grown in either enantiomeric forms. Recent striking experimental observations reveal a subtle difference in the enantioselectivity of the PdGa(111) and the PdGa(-1-1-1) termination with respect to adsorption of 9-ethynylphenanthrene. This poster presents the challenges recently encountered by atomistic modeling (based on density functional theory and on Monte Carlo simulations) in unravelling the origin of the experimental findings.
| MAT-22 |
Liquid Layering Effects on the Kapitza Resistance Between Few-Layer Graphene and Water, Dmitry Alexeev (ETH Zurich, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
MAT-22
Liquid Layering Effects on the Kapitza Resistance Between Few-Layer Graphene and Water, Dmitry Alexeev (ETH Zurich, Switzerland)
Co-authors: Jie Chen (ETH Zurich, Switzerland); Jens H. Walther (ETH Zurich, Switzerland/ Technical University of Denmark, Denmark); Konstantinos P. Giapis (California Institute of Technology, USA); Petros Koumoutsakos (ETH Zurich, Switzerland)
Kapitza resistance (R) between few-layer graphene (FLG) and water is systematically studied using molecular dynamics simulations. In contrast to monoatomic liquid/solid interfaces, R between FLG and water is found to decrease with temperature. The R exhibits a distinct dependence on the thickness of the FLG and the water layer that is attributed to large differences in their phonon mean free path. The density layering of the water near the interface has a significant impact on R with higher water density corresponding to a lower R. Based on these findings we propose two mechanisms to regulate the water layering as means to engineer the thermal transport properties of solid-liquid interfaces.
