Preface thirty one years ago, because of the dramatic increase in the power and utility of computersimulations, the University of Georgia formed the first institutional unit devoted to the application of simulations ...
Preface thirty one years ago, because of the dramatic increase in the power and utility of computersimulations, the University of Georgia formed the first institutional unit devoted to the application of simulations in research and teaching: the Center for simulational physics. then, as the international simulations community expanded further, we sensed the need for a meeting place for both experienced simulators and newcomers to discuss inventive algorithms and recent results in an environment that promoted lively discussion. As a consequence, the Center for simulational physics established an annual workshop series on recentdevelopments in computersimulationstudies in condensedmatterphysics. this year's highly interactive workshop was the 30th in the series marking our efforts to promote high quality research in simulational physics. the continued interest shown by the scientific community amply demonstrates the useful purpose that these meetings have served. the latest workshop was held at the University of Georgia from February 20-24, 2017 and served to mark three decades of successful and highly interactive workshops. these Proceedings provide a 'status report' on a number of important topics. this on-line 'volume' is published withthe goal of timely dissemination of the material to a wider audience. these Proceedings contain both invited papers and contributed presentations on problems in both classical and quantum condensedmatterphysics. the day prior to the workshop we co-hosted, together with Riken, Japan, a Tutorial on the simulations management tool OACIS, and the Proceedings begins with an overview of the tutorial material. the workshop topics, as usual, ranged from hard and soft condensedmatter to biologically inspired problems and purely methodological advances. While familiar topics like phase transitions were still on display, the trends in biophysics, dynamical behavior and complex systems demonstrated the continuing progression in the foc
thirty years ago, because of the dramatic increase in the power and utility of computersimulations, the University of Georgia formed the first institutional unit devoted to the application of simulations in research ...
thirty years ago, because of the dramatic increase in the power and utility of computersimulations, the University of Georgia formed the first institutional unit devoted to the application of simulations in research and teaching: the Center for simulational physics. then, as the international simulations community expanded further, we sensed the need for a meeting place for both experienced simulators and newcomers to discuss inventive algorithms and recent results in an environment that promoted lively discussion. As a consequence, the Center for simulational physics established an annual workshop series on recentdevelopments in computersimulationstudies in condensedmatterphysics. this year's highly interactive workshop was the 29th in the series marking our efforts to promote high quality research in simulational physics. the continued interest shown by the scientific community amply demonstrates the useful purpose that these meetings have served. the latest workshop was held at the University of Georgia from February 22-26, 2016. It served to mark the 30th Anniversary of the founding of the Center for simulational physics. In addition, during this workshop we celebrated the 60th birthday of our esteemed colleague Prof. H.-Bernd Schuttler. Bernd has not only contributed to the understanding of strongly correlated electron system, but has made seminal contributions to systems biology through the introduction of modern methods of computational physics. these Proceedings provide a 'status report' on a number of important topics. this on-line 'volume' is published withthe goal of timely dissemination of the material to a wider audience. this program was supported in part by the President's Venture Fund through the generous gifts of the University of Georgia Partners and other donors. We also wish to offer thanks to the Office of the Vice-President for Research, the Franklin College of Arts and Sciences, and the IBM Corporation for partial support of this year's
Determining which microstates generated by a thermodynamic simulation are representative of the ensemble for which sampling is desired is a ubiquitous, underspecified problem. Artificial neural networks are one type o...
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Determining which microstates generated by a thermodynamic simulation are representative of the ensemble for which sampling is desired is a ubiquitous, underspecified problem. Artificial neural networks are one type of machine learning algorithm that can provide a reproducible way to apply pattern recognition heuristics to underspecified problems. Here we use the open-source TensorFlow machine learning library and apply it to the problem of identifying which hypothetical observation sequences from a computersimulation are "equilibrated" and which are not. We generate training populations and test populations of observation sequences with embedded linear and exponential correlations. We train a twoneuron artificial network to distinguish the correlated and uncorrelated sequences. We find that this simple network is good enough for > 98% accuracy in identifying exponentially-decaying energy trajectories from molecular simulations.
Using an atomistic model that treats both translational and spin degrees of freedom, we have performed combined molecular and spin dynamics simulations to study dynamic properties of BCC iron with varying vacancy conc...
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Using an atomistic model that treats both translational and spin degrees of freedom, we have performed combined molecular and spin dynamics simulations to study dynamic properties of BCC iron with varying vacancy concentrations. Atomic interactions are described by an empirical many-body potential while spin interactions are handled with a Heisenberg-like Hamiltonian with a coordinate dependent exchange interaction. By calculating the Fourier transform of spatial and temporal correlation functions, vibrational and magnetic excitations have been studied. the creation of vacancies in the material has shown splitting of the characteristic transverse spin-wave excitations, indicating the production of additional excitation modes. By merging two vacancies to form a nearest neighbor pair, we find that these modes become more distinct. Investigation of longitudinal spin-wave excitations reveals interactions between constituent components of the split transverse excitations.
the canonical technique for Monte Carlo simulations in statistical physics is importance sampling via a suitably constructed Markov chain. While such approaches are quite successful, they are not particularly well sui...
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the canonical technique for Monte Carlo simulations in statistical physics is importance sampling via a suitably constructed Markov chain. While such approaches are quite successful, they are not particularly well suited for parallelization as the chain dynamics is sequential, and if replicated chains are used to increase statistics each of them relaxes into equilibrium with an intrinsic time constant that cannot be reduced by parallel work. Population annealing is a sequential Monte Carlo method that simulates an ensemble of system replica under a cooling protocol. the population element makes it naturally well suited for massively parallel simulations, and bias can be systematically reduced by increasing the population size. We present an implementation of population annealing on graphics processing units and discuss its behavior for different systems undergoing continuous and first-order phase transitions.
the proceedings contain 19 papers. the topics discussed include: the zeros of the energy probability distribution - a new way to study phase transitions;accuracy and transferability of ab initio electronic band struct...
the proceedings contain 19 papers. the topics discussed include: the zeros of the energy probability distribution - a new way to study phase transitions;accuracy and transferability of ab initio electronic band structure calculations for doped BiFeO3;collective motion in repulsive self-propelled particles in confined geometries;interface of topological insulator Bi2Se3 with As2Te3;high resolution Monte Carlo study of the Domb-Joyce model;applying renormalization group to quantum walks;an iterative aggregation and disaggregation approach to the calculation of steady state distributions of continuous processes;universality and phase diagrams of the Baxter-Wu model in a crystal field: spin-1 and spin-3/2;application of artificial neural networks to identify equilibration in computersimulations;an open-source job management framework for parameter-space exploration: OACIS;a study of vibrating nanotubes with additional adsorbed masses;interactions between proteins and poly(ethylene-glycol) investigated using molecular dynamics simulations;combined molecular and spin dynamics simulation of bcc iron with lattice vacancies;structure of transition metal clusters: a force-biased Monte Carlo approach;transition barrier at a first-order phase transition in the canonical and microcanonical ensemble;shape matters: the case for ellipsoids and ellipsoidal water;Yaldram-Khan model with CO and N desorption;and population annealing: massively parallel simulations in statistical physics.
the Wang-Landau algorithm is an entropic sampling method that incoroporates an update factor ln f(i), which introduces a self-avoidance tendency into the random walk. Continued sampling at constant ln f(i) leads to a ...
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the Wang-Landau algorithm is an entropic sampling method that incoroporates an update factor ln f(i), which introduces a self-avoidance tendency into the random walk. Continued sampling at constant ln f(i) leads to a steady state estimate of the density of states ln g(i) (E). We find numerically that the difference between ln g(i) (E) and the true density of states ln g (E) is proportional to the update factor.
Nature often arranges atoms in the shape of perfect crystals, but sometimes she creates defects and multiple domains. the optimal crystal shape at zero kelvin can be found via the Wulff construction, which can be only...
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Nature often arranges atoms in the shape of perfect crystals, but sometimes she creates defects and multiple domains. the optimal crystal shape at zero kelvin can be found via the Wulff construction, which can be only be carried out analytically for those trivial cases where next nearest neighbour interactions can be neglected. For our system of interest - videlicit the HCP non-Bravais case, numerical simulation is needed. this system is of relevance because we are modeling helium crystals. We have modeled two adjacent crystallites with different orientations in contact creating twist or tilt grain boundaries, and calculated the surface energy of the interface. Experience gained from several aspects of this project have a wider applications, including the condensedmattersimulation application to sample construction for multi-domain crystals, and a visualization one for representation in the presence of grain boundaries. the optimization of sample shapes into their groundstates is also related to wavefront optimization in multimirror telescopes.
the proceedings contain 22 papers. the topics discussed include: flat-histogram methods in quantum Monte Carlo simulations: application to the t-j model;manifest and subtle cyclic behavior in nonequilibrium steady sta...
the proceedings contain 22 papers. the topics discussed include: flat-histogram methods in quantum Monte Carlo simulations: application to the t-j model;manifest and subtle cyclic behavior in nonequilibrium steady states;thermodynamics and phase coexistence in nonequilibrium steady states;an answer checking method for quantum annealers;stable knots in the phase diagram of semiexible polymers: a topological order parameter?;determination of shape-reactivity relationships in Al-nanoclusters;a mean-field analysis of the simple model of evolving open systems;comparing atomistic and coarse{grained simulations of P3HT;and simulation and visualization of crystal shapes and interfaces.
the Computational physics group at the Technion has developed a visualization code, AViz, for atomistic visualization. AViz can visualize atoms, vector spins, quadrupoles, electronic densities, polymers and more. the ...
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