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Speeding-up Ab Initio Molecular Dynamics with Hybrid Functionals using Adaptively Compressed Exchange Operator based Multiple TimesteppingAug 22 2019Ab initio molecular dynamics (AIMD) simulations using hybrid density functionals and plane waves are of great interest owing to the accuracy of this approach in treating condensed matter systems. On the other hand, such AIMD calculations are not routinely ... More

Applying machine learning optimization methods to the production of a quantum gasAug 22 2019We apply three machine learning strategies to optimize the atomic cooling processes utilized in the production of a Bose-Einstein condensate (BEC). For the first time, we optimize both laser cooling and evaporative cooling mechanisms simultaneously. We ... More

Seismic tomography using variational inference methodsAug 22 2019Seismic tomography is a methodology to image the interior of solid or fluid media, and is often used to map properties in the subsurface of the Earth. In order to better interpret the resulting images it is important to assess imaging uncertainties. Since ... More

A parametric finite element method for solid-state dewetting problems in three dimensionsAug 22 2019We propose a parametric finite element method (PFEM) for efficiently solving the morphological evolution of solid-state dewetting of thin films on a flat rigid substrate in three dimensions (3D). The interface evolution of the dewetting problem in 3D ... More

Small polarons and the Janus nature of $\text{TiO}_\text{2}(110)$Aug 21 2019Polarons are ubiquitous in many semiconductors and have been linked with conductivity and optical response of materials for photovoltaics and heterogeneous catalysis, yet how surface polarons influence adsorption remains unclear. Here, by modelling the ... More

Inverse Structural Design of Graphene/Boron Nitride Hybrids by Regressional GANAug 21 2019Inverse design of materials with desired properties is currently laborious and heavily relies on intuition of researchers through a trial-and-error process. The massive combinational spaces due to the constituent elements and their structural configurations ... More

Data-driven model reduction, Wiener projections, and the Mori-Zwanzig formalismAug 21 2019First-principles models of complex dynamic phenomena often have many degrees of freedom, only a small fraction of which may be scientifically relevant or observable. Reduced models distill such phenomena to their essence by modeling only relevant variables, ... More

Effective transport properties of conformal Voronoi-bounded columns via recurrent boundary element expansionsAug 21 2019Effective transport properties of heterogeneous structures are predicted by geometric microstructural parameters, but these can be difficult to calculate. Here, a boundary element code with a recurrent series method accurately and efficiently determines ... More

Symmetry-preserving WENO limitersAug 21 2019Weighted essentially non-oscillatory (WENO) reconstruction schemes are presented that preserve cylindrical symmetry for radial flows on an equal-angle polar mesh. These new WENO schemes are used with a Lagrangian discontinuous Galerkin (DG) hydrodynamic ... More

A linear-scaling algorithm for rapid computation of inelastic transitions in the presence of multiple electron scatteringAug 20 2019Strong multiple scattering of the probe in scanning transmission electron microscopy (STEM) means image simulations are usually required for quantitative interpretation and analysis of elemental maps produced by electron energy-loss spectroscopy (EELS). ... More

Chaotic wave packet spreading in two-dimensional disordered nonlinear latticesAug 20 2019We reveal the generic characteristics of wave packet delocalization in two-dimensional nonlinear disordered lattices by performing extensive numerical simulations in two basic disordered models: the Klein-Gordon system and the discrete nonlinear Schr\"{o}dinger ... More

ElectroLens: Understanding Atomistic Simulations Through Spatially-resolved Visualization of High-dimensional FeaturesAug 20 2019In recent years, machine learning (ML) has gained significant popularity in the field of chemical informatics and electronic structure theory. These techniques often require researchers to engineer abstract "features" that encode chemical concepts into ... More

Sparse sampling approach to efficient ab initio calculations at finite temperatureAug 20 2019Efficient ab initio calculations of correlated materials at finite temperature require compact representations of the Green's functions both in imaginary time and Matsubara frequency. In this paper, we introduce a general procedure which generates sparse ... More

The effects of clinically-derived parametric data uncertainty in patient-specific coronary simulations with deformable wallsAug 20 2019Cardiovascular simulations are increasingly used for non-invasive diagnosis of cardiovascular disease, to guide treatment decisions, and in the design of medical devices. Quantitative assessment of the variability of simulation outputs due to input uncertainty ... More

Machine learning configuration interaction for ab initio potential energy curvesAug 20 2019The concept of machine learning configuration interaction (MLCI) [J. Chem. Theory Comput. 2018, 14, 5739], where an artificial neural network (ANN) learns on the fly to select important configurations, is further developed so that accurate ab initio potential ... More

Sampling protein-ligand binding pathways to recover crystallographic binding poses using interactive molecular dynamics in virtual realityAug 20 2019Using molecular dynamics (MD) to simulate drug binding & unbinding is a challenge. Because it requires sampling rugged energy landscapes that separate bound and unbound states, it has a high cost and consumes significant computational resources. Here, ... More

Machine-learning interatomic potential for radiation damage and defects in tungstenAug 20 2019We introduce a machine-learning interatomic potential for tungsten using the Gaussian Approximation Potential framework. We specifically focus on properties relevant for simulations of radiation-induced collision cascades and the damage they produce, ... More

Cost Reduction of Swapping Bonds Part in Anisotropic Tensor Renormalization GroupAug 20 2019The bottleneck part of anisotropic tensor renormalization group (ATRG) is a swapping bonds part which consists of a contraction of two tensors and a partial singular value decomposition of a matrix, and their computational costs are $O(\chi^{2d+1})$, ... More

Energy-level alignment at organic/inorganic interfaces from first principles: Example of poly(\emph{para}-phenylene) / rock-salt ZnO(100)Aug 20 2019By means of full-potential all-electron density-functional theory and many-body perturbation theory, we compute the band alignment at a prototypical hybrid inorganic/organic interface. The electronic properties of a model system built of poly(\emph{para}-phenylene) ... More

Population-based metaheuristic optimization in neutron optics and shielding designAug 20 2019Population-based metaheuristic algorithms are powerful tools in the design of neutron scattering instruments and the use of these types of algorithms for this purpose is becoming more and more commonplace. Today there exists a wide range of algorithms ... More

Achieving large-scale or high-resolution topology optimization based on Modified BESO and XEFMAug 20 2019To solve large-scale or high-resolution topology optimization problem, a novel algorithm is developed based on modified bi-directional evolutionary structure optimization (BESO) and extended finite element method (XFEM). Within XFEM, a set of enriched ... More

Three-dimensional graphene networks modified with acetylenic linkages for high-performance optoelectronics and Li-ion battery anode materialAug 20 2019Searching for three-dimensional(3D) semiconducting carbon allotropes with proper bandgaps and excellent optoelectronic properties is always the chasing goal for the new emerging all-carbon optoelectronics. On the other side, 3D carbon materials have also ... More

Beyond the Coulson-Fischer point: Characterizing single excitation CI and TDDFT for excited states in single bond dissociationsAug 19 2019Linear response time dependent density functional theory (TDDFT), which builds upon configuration interaction singles (CIS) and TD-Hartree-Fock (TDHF), is the most widely used class of excited state quantum chemistry methods and is often employed to study ... More

A combined on-the-fly/interpolation procedure for evaluating energy values needed in molecular simulationsAug 19 2019We propose an algorithm for molecular dynamics or Monte Carlo simulations that uses an interpolation procedure to estimate potential energy values from energies and gradients evaluated previously at points of a simplicial mesh. We chose an interpolation ... More

A combined on-the-fly/interpolation procedure for evaluating energy values needed in molecular simulationsAug 19 2019Aug 20 2019We propose an algorithm for molecular dynamics or Monte Carlo simulations that uses an interpolation procedure to estimate potential energy values from energies and gradients evaluated previously at points of a simplicial mesh. We chose an interpolation ... More

Machine learning the computational cost of quantum chemistryAug 19 2019Computational quantum mechanics based molecular and materials design campaigns consume increasingly more high-performance compute resources, making improved job scheduling efficiency desirable in order to reduce carbon footprint or wasteful spending. ... More

Electron-phonon coupling and hot electron thermalization in titanium nitrideAug 19 2019We have studied the thermalization of hot carriers in both pristine and defective titanium nitride (TiN) using a two-temperature model. All parameters of this model, including the electron-phonon coupling parameter, were obtained from first-principles ... More

Accelerated relaxation in disordered solids under cyclic loading with alternating shear orientationAug 18 2019The effect of alternating shear orientation during cyclic loading on the relaxation dynamics in disordered solids is examined using molecular dynamics simulations. The model glass was initially prepared by rapid cooling from the liquid state and then ... More

Wavelet-based parallel dynamic mesh adaptation for magnetohydrodynamics in the AMROC frameworkAug 17 2019Computational magnetohydrodynamics (MHD) for space physics has become an essential area in understanding the multiscale dynamics of geophysical and astrophysical plasma processes, partially motivated by the lack of space data. Full MHD simulations are ... More

On the boundary condition and related instability in the Smoothed Particle HydrodynamicsAug 17 2019In this work, we explore various relevant aspects of the Smoothed Particle Hydrodynamics regarding Burger's equation. The stability, precision, and efficiency of the algorithm are investigated in terms of different implementations. In particular, we argue ... More

Machine learning the physical non-local exchange-correlation functional of density-functional theoryAug 16 2019We train a neural network as the universal exchange-correlation functional of density-functional theory that simultaneously reproduces both the exact exchange-correlation energy and potential. This functional is extremely non-local, but retains the computational ... More

A Shift Selection Strategy for Parallel Shift-Invert Spectrum Slicing in Symmetric Self-Consistent Eigenvalue ComputationAug 16 2019The central importance of large scale eigenvalue problems in scientific computation necessitates the development massively parallel algorithms for their solution. Recent advances in dense numerical linear algebra have enabled the routine treatment of ... More

Modeling of rigidity dependent CORSIKA simulations for GRAPES-3Aug 16 2019The GRAPES-3 muon telescope located in Ooty, India records 4x10^9 muons daily. These muons are produced by interaction of primary cosmic rays (PCRs) in the atmosphere. The high statistics of muons enables GRAPES-3 to make precise measurement of various ... More

Matrix Lie Maps and Neural Networks for Solving Differential EquationsAug 16 2019The coincidence between polynomial neural networks and matrix Lie maps is discussed in the article. The matrix form of Lie transform is an approximation of the general solution of the nonlinear system of ordinary differential equations. It can be used ... More

Machine learning magnetic parameters from spin configurationsAug 16 2019Estimation of Hamiltonian is key to our understanding of everything in quantum mechanics. For magnetic systems, in particular, the task can be daunting due to the exponentially large Hilbert space. Here, we show that modern machine learning architectures, ... More

A deep-learning-based surrogate model for data assimilation in dynamic subsurface flow problemsAug 16 2019A deep-learning-based surrogate model is developed and applied for predicting dynamic subsurface flow in channelized geological models. The surrogate model is based on deep convolutional and recurrent neural network architectures, specifically a residual ... More

Metallic liquid H3O in a thin-shell zone inside Uranus and NeptuneAug 16 2019The Solar System harbors deep unresolved mysteries despite centuries-long study. A highly intriguing case concerns anomalous non-dipolar and non-axisymmetric magnetic fields of Uranus and Neptune that have long eluded explanation by the prevailing theory. ... More

Dynamics of Hot Bose-Einstein Condensates: stochastic Ehrenfest relations for number and energy dampingAug 16 2019Describing high-temperature Bose gases poses a long-standing theoretical challenge. We present exact stochastic Ehrenfest relations for the stochastic projected Gross-Pitaevskii equation, including both number and energy damping mechanisms, and all projector ... More

Neural network for phase diagrams of polymer-containing liquid mixturesAug 15 2019Polymer-containing liquid mixtures can exhibit macroscopic phase separation and microphase separation. The diversity of the phase behavior exponentially increases when altering the polymer architecture or adding salt ions, yet exploring and modeling this ... More

Inflation deployed torus-shaped solar sail accelerated via thermal desorption of coatingAug 15 2019Aug 22 2019A torus-shaped sail consists of a reflective membrane attached to an inflatable torus-shaped rim. The sail's deployment from its stowed configuration is initiated by introducing inflation pressure into the toroidal rim with an attached circular flat membrane ... More

Inflation deployed torus-shaped solar sail accelerated via thermal desorption of coatingAug 15 2019A torus-shaped sail consists of a reflective membrane attached to an inflatable torus-shaped rim. The sail's deployment from its stowed configuration is initiated by introducing inflation pressure into the toroidal rim with an attached circular flat membrane ... More

Electromagnetic full-$f$ gyrokinetics in the tokamak edge with discontinuous Galerkin methodsAug 15 2019Aug 16 2019We present an energy-conserving discontinuous Galerkin scheme for the full-$f$ electromagnetic gyrokinetic system in the long-wavelength limit. We use the symplectic formulation and solve directly for $\partial A_\parallel/\partial t$, the inductive component ... More

Electromagnetic full-$f$ gyrokinetics in the tokamak edge with discontinuous Galerkin methodsAug 15 2019We present an energy-conserving discontinuous Galerkin scheme for the full-$f$ electromagnetic gyrokinetic system in the long-wavelength limit. We use the symplectic formulation and solve directly for $\partial A_\parallel/\partial t$, the inductive component ... More

Fast Three-dimensional Opto-acoustic Simulation for Linear Array with Rectangular ElementsAug 15 2019Aug 16 2019Simulation involves predicting responses of a physical system. In this article, we simulate opto-acoustic signals generated in a three-dimensional volume due to absorption of an optical pulse. A separable computational model is developed that permits ... More

Fast Three-dimensional Opto-acoustic Simulation for Linear Array with Rectangular ElementsAug 15 2019Simulation involves predicting responses of a physical system. In this article, we simulate opto-acoustic signals generated in a three-dimensional volume due to absorption of an optical pulse. A separable computational model is developed that permits ... More

Liquid-Hextic-Solid Phase Transition of a Hard-Core Lattice Gas with Third Neighbor ExclusionAug 15 2019The determination of phase behavior and, in particular, the nature of phase transitions in two-dimensional systems is often clouded by finite size effects and by access to the appropriate thermodynamic regime. We address these issues using an alternative ... More

Cosmological N-body simulations: a challenge for scalable generative modelsAug 15 2019Deep generative models, such as Generative Adversarial Networks (GANs) or Variational Autoencoders have been demonstrated to produce images of high visual quality. However, the existing hardware on which these models are trained severely limits the size ... More

Cascaded Lattice Boltzmann Modeling and Simulations of Three-Dimensional Non-Newtonian Fluid FlowsAug 15 2019Non-Newtonian fluid flows, especially in three dimensions (3D), arise in numerous settings of interest to physics. Prior studies using the lattice Boltzmann method (LBM) of such flows have so far been limited to mainly to two dimensions and used less ... More

Local Vorticity Computation in Double Distribution Functions based Lattice Boltzmann Methods for Flow and Scalar TransportAug 14 2019Computation of vorticity in conjunction with the strain rate tensor, plays an important role in fluid mechanics in vortical structure identification and in the modeling of various complex fluids. For the simulation of flows accompanied by the advection-diffusion ... More

Density Effects on the Post-shock Turbulence Structure and DynamicsAug 14 2019Turbulence structure resulting from multi-fluid or multi-species, variable-density isotropic turbulence interaction with a Mach 2 shock is studied using turbulence-resolving shock-capturing simulations and Eulerian (grid) and Lagrangian (particle) methods. ... More

Quasi-Diabatic Scheme for Non-adiabatic On-the-fly SimulationsAug 14 2019This paper provides the first ab-initio on-the-fly example of using the Quasi-Diabatic (QD) scheme for non-adiabatic simulations with diabatic dynamics approaches. The QD scheme provides a seamless interface between diabatic quantum dynamics approaches ... More

Substrate effects on charged defects in two-dimensional materialsAug 14 2019Two-dimensional (2D) materials are strongly affected by the dielectric environment including substrates, making it an important factor in designing materials for quantum and electronic technologies. Yet, first-principles evaluation of charged defect energetics ... More

Comparing quantum, molecular and continuum models for graphene at large deformationsAug 14 2019In this paper, the validity and accuracy of three interatomic potentials, commonly used to study carbon nanostructures in molecular dynamics, and the continuum shell model of Ghaffari and Sauer [1] are investigated. The mechanical behavior of single-layered ... More

Aluminum oxide phase transitions from cluster to nanoparticleAug 14 2019Aluminum oxide nanoparticles are increasingly sought in numerous technological applications. But, their structural properties can hardly be controlled during the synthesis because phase transitions occurs as the nanoparticle grows. Numerical simulation ... More

Fully-resolved wave-structure interaction simulations of a submerged cylindrical point absorber with three degrees of freedomAug 14 2019In this paper we present a fictitious domain Brinkman penalization (FD/BP) method for simulating wave-structure interactions (WSI) of a submerged cylindrical point absorber with three free degrees of freedom (DOF). The submerged buoy is tethered using ... More

Random walk on a lattice in the presence of obstacles: The short-time transient regime, anomalous diffusion and crowdingAug 14 2019The diffusion of a particle in a crowded environment typically proceeds through three regimes: for very short times the particle diffuses freely until it collides with an obstacle for the first time, while for very long times diffusion the motion is Fickian ... More

Multilevel and multifidelity uncertainty quantification for cardiovascular hemodynamicsAug 13 2019Standard approaches for uncertainty quantification (UQ) in cardiovascular modeling pose challenges due to the large number of uncertain inputs and the significant computational cost of realistic 3D simulations. We propose an efficient UQ framework utilizing ... More

Reaction coordinates and rate constants for liquid droplet nucleation: quantifying the interplay between driving force and memoryAug 13 2019In this work we revisit the classic problem of homogeneous nucleation of a liquid droplet in a supersaturated vapor phase. We consider this at different extents of the driving force, which here is the extent of supersaturation, and calculate a reaction ... More

First-principles many-body non-additive polarization energies from monomer and dimer calculations only : A case study on waterAug 13 2019The many-body polarization energy is the major source of non-additivity in strongly polar systems such as water. This non-additivity is often considerable and must be included, if only in an average manner, to correctly describe the physical properties ... More

Magnetization current simulation of high temperature bulk superconductors using A-V-A formula based iterative algorithm methodAug 13 2019In this work we will introduce the A-V-A formula based iterative algorithm method (IAM) for simulating the magnetization of superconductors. This new method is for the first time tested in simulating both the critical state model and the flux creep model ... More

Numerical benchmarking of fluid-rigid body interactionsAug 13 2019We propose a fluid-rigid body interaction benchmark problem, consisting of a solid spherical obstacle in a Newtonian fluid, whose centre of mass is fixed but is free to rotate. A number of different problems are defined for both two and three spatial ... More

DL-PDE: Deep-learning based data-driven discovery of partial differential equations from discrete and noisy dataAug 13 2019In recent years, data-driven methods have been utilized to learn dynamical systems and partial differential equations (PDE). However, major challenges remain to be resolved, including learning PDE under noisy data and limited discrete data. To overcome ... More

Giant temperature dependence of the Mott gap size in 1T-TaS 2 : a molecular dynamics studyAug 13 2019The lattice thermodynamics of 1T-TaS 2 , e.g. the spontaneous formation of periodic distortion and vibrations around the equilibrium position, is calculated by ab initio molecular dynamics. Based on that, the finite-temperature electronic structure is ... More

Giant temperature dependence of the Mott gap size in 1T-TaS$_2$ : a molecular dynamics studyAug 13 2019Aug 15 2019The lattice thermodynamics of 1T-TaS$_2$, e.g. the spontaneous formation of periodic distortion and vibrations around the equilibrium position, is calculated by ab initio molecular dynamics. Based on that, the finite-temperature electronic structure is ... More

Exact Solov'ev equilibrium with an arbitrary boundaryAug 13 2019Exact Solov'ev equilibria for arbitrary plasma cross-sections are calculated using a constrained least-squares method. The boundary, with or without $X$-points, can be specified with an arbitrarily large number of constraints to ensure an accurate representation. ... More

Exact Solov'ev equilibrium with an arbitrary boundaryAug 13 2019Aug 14 2019Exact Solov'ev equilibria for arbitrary plasma cross-sections are calculated using a constrained least-squares method. The boundary, with or without $X$-points, can be specified with an arbitrarily large number of constraints to ensure an accurate representation. ... More

Implementation of contact angles in the pseudopotential lattice Boltzmann simulations with curved boundariesAug 13 2019The pseudopotential multiphase lattice Boltzmann (LB) model is a popular model in the LB community for simulating multiphase flows. When the multiphase modeling involves a solid boundary, a numerical scheme is required to simulate the contact angle at ... More

Enabling Simulation of High-Dimensional Micro-Macro Biophysical Models through Hybrid CPU and Multi-GPU ParallelismAug 12 2019Micro-macro models provide a powerful tool to study the relationship between microscale mechanisms and emergent macroscopic behavior. However, the detailed microscopic modeling may require tracking and evolving a high-dimensional configuration space at ... More

Dust charging in dynamic ion wakesAug 12 2019Micron-sized dust grains have been successfully employed as non-perturbative probes to measure variations in plasma conditions on small spatial scales, such as those found in plasma sheaths. The dynamics of the grains can be used to map the forces due ... More

Tensor-based EDMD for the Koopman analysis of high-dimensional systemsAug 12 2019Recent years have seen rapid advances in the data-driven analysis of dynamical systems based on Koopman operator theory -- with extended dynamic mode decomposition (EDMD) being a cornerstone of the field. On the other hand, low-rank tensor product approximations ... More

Advances in electron backscatter diffractionAug 12 2019We present a few recent developments in the field of electron backscatter diffraction (EBSD). We highlight how open source algorithms and open data formats can be used to rapidly to develop microstructural insight of materials. We include use of AstroEBSD ... More

A review on Deep Reinforcement Learning for Fluid MechanicsAug 12 2019Deep reinforcement learning (DRL) has recently been adopted in a wide range of physics and engineering domains for its ability to solve decision-making problems that were previously out of reach due to a combination of non-linearity and high dimensionality. ... More

An implicit $ P $-multigrid flux reconstruction method for simulation of locally preconditioned unsteady Navier-Stokes equations at low Mach numbersAug 11 2019We develop a $ P $-multigrid solver to simulate locally preconditioned unsteady compressible Navier-Stokes equations at low Mach numbers with implicit high-order methods. Specifically, the high-order flux reconstruction/correction procedure via reconstruction ... More

Quantum interference engineering of nanoporous graphene for carbon nanocircuitryAug 11 2019Bottom-up prepared carbon nanostructures appear as promising platforms for future carbon-based nanoelectronics, due to their atomically precise and versatile structure. An important breakthrough is the recent preparation of nanoporous graphene (NPG) as ... More

Three-dimensional Electro-convective Vortices in Cross-flowAug 11 2019The study focuses on the 3D electro-hydrodynamic (EHD) instability for flow between to parallel electrodes with unipolar charge injection with and without cross-flow. Lattice Boltzmann Method (LBM) with two-relaxation time (TRT) model is used to study ... More

Whole device gyrokinetic simulations using unstructured meshes in realistic tokamak geometryAug 10 2019In this work, we have formulated and implemented the mixed unstructured mesh-based finite element-Fourier spectrum scheme for gyrokinetic simulation in realistic tokamak geometry. An efficient particle deposition scheme using an intermediate grid as the ... More

Predicting Rare Events in Multiscale Dynamical Systems using Machine LearningAug 10 2019We study the problem of rare event prediction for a class of slow-fast nonlinear dynamical systems. The state of the system of interest is described by a slow process, whereas a faster process drives its evolution. By taking advantage of recent advances ... More

Implementation of Morse-Witten theory for a polydisperse wet 2D foam simulationAug 10 2019The Morse-Witten theory (D. Morse and T. Witten, EPL 22 (1993) 549-555) provides a formulation for the inter-bubble forces and corresponding deformations in a liquid foam, accurate in the limit of high liquid fraction. Here we show how the theory may ... More

Iterative optimization of photonic crystal nanocavity designs by using deep neural networksAug 10 2019Devices based on two-dimensional photonic-crystal (2D-PC) nanocavities, which are defined by their air hole patterns, usually require a high quality (Q) factor to achieve high performance. We demonstrate that hole patterns with very high Q factors can ... More

Lagrangian Dynamic Mode Decomposition for Construction of Reduced-Order Models of Advection-Dominated PhenomenaAug 10 2019Proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) are two complementary singular-value decomposition (SVD) techniques that are widely used to construct reduced-order models (ROMs) in a variety of fields of science and engineering. ... More

Robust data-driven approach for predicting the configurational energy of high entropy alloysAug 10 2019High entropy alloys (HEAs) have been increasingly attractive as promising next-generation materials due to their various excellent properties. It's necessary to essentially characterize the degree of chemical ordering and identify order-disorder transitions ... More

Improved Coupling of Hydrodynamics and Nuclear Reactions via Spectral Deferred CorrectionsAug 10 2019Simulations in stellar astrophysics involve the coupling of hydrodynamics and nuclear reactions under a wide variety of conditions, from simmering convective flows to explosive nucleosynthesis. Numerical techniques such as operator splitting (most notably ... More

MAESTROeX: A Massively Parallel Low Mach Number Astrophysical SolverAug 09 2019We present MAESTROeX, a massively parallel solver for low Mach number astrophysical flows. The underlying low Mach number equation set allows for efficient, long-time integration for highly subsonic flows compared to compressible approaches. MAESTROeX ... More

Learning physics-based reduced-order models for a single-injector combustion processAug 09 2019This paper presents a physics-based data-driven method to learn predictive reduced-order models (ROMs) from high-fidelity simulations, and illustrates it in the challenging context of a single-injector combustion process. The method combines the perspectives ... More

Learning physics-based reduced-order models for a single-injector combustion processAug 09 2019Aug 13 2019This paper presents a physics-based data-driven method to learn predictive reduced-order models (ROMs) from high-fidelity simulations, and illustrates it in the challenging context of a single-injector combustion process. The method combines the perspectives ... More

An Adaptive ALE Scheme for Non-Ideal Compressible-Fluid Dynamics over Dynamic Unstructured MeshesAug 09 2019This paper investigates the application of mesh adaptation techniques in the Non-Ideal Compressible Fluid Dynamic (NICFD) regime, a region near the vapor-liquid saturation curve where the flow behavior significantly departs from the ideal gas model, as ... More

Efficient implementation of Cluster Expansion models in surface Kinetic Monte Carlo simulations with lateral interactions: Subtraction Schemes, Supersites and the Supercluster ContractionAug 09 2019While lateral interaction models for reactions at surfaces have steadily gained popularity and grown in terms of complexity, their use in chemical kinetics has been impeded by the low performance of current KMC algorithms. The origins of the additional ... More

Efficient Simulation of Fluid Flow and Transport in Heterogeneous Media Using Graphics Processing Units (GPUs)Aug 09 2019Networks of interconnected resistors, springs and beams, or pores are standard models of studying scalar and vector transport processes in heterogeneous materials and media, such as fluid flow in porous media, and conduction, deformations, and electric ... More

Simulation of Polymer Foaming using the Lattice Boltzmann MethodAug 08 2019This paper presents a 3D lattice Boltzmann model (LBM) for simulation of polymer foaming processes. The model incorporates many of the essential aspects of foaming phenomena: gas diffusion into nucleated bubbles, bubble dynamics and coalescence, surface ... More

Prediction of C7N6 and C9N4: Stable and strong porous carbon-nitride nanosheets with attractive electronic and optical propertiesAug 08 2019In this work, three novel porous carbon-nitride nanosheets with C7N6, C9N4 and C10N3 stoichiometries are predicted. First-principles simulations were accordingly employed to evaluate stability and explore the mechanical, electronic and optical properties. ... More

Prediction of C7N6 and C9N4: Stable and strong porous carbon-nitride nanosheets with attractive electronic and optical propertiesAug 08 2019Aug 16 2019In this work, three novel porous carbon-nitride nanosheets with C7N6, C9N4 and C10N3 stoichiometries are predicted. First-principles simulations were accordingly employed to evaluate stability and explore the mechanical, electronic and optical properties. ... More

UKRmol+: a suite for modelling of electronic processes in molecules interacting with electrons, positrons and photons using the R-matrix methodAug 08 2019UKRmol+ is a new implementation of the UK R-matrix electron-molecule scattering code. Key features of the implementation are the use of quantum chemistry codes such as Molpro to provide target molecular orbitals; the optional use of mixed Gaussian -- ... More

A Unified Approach for Deriving Optimal Finite DifferencesAug 08 2019A unified approach to derive optimal finite differences is presented which combines three critical elements for numerical performance especially for multi-scale physical problems, namely, order of accuracy, spectral resolution and stability. The resulting ... More

A $π$-shaped Quantum Device for Implementation of Bell States in Solid State EnvironmentAug 07 2019Electronic spin-qubit is key ingredient for quantum information processing in a solid state environment. We present a $\pi$-shaped two-qubit entanglement device capable of measuring the resultant states in Bell basis. In our device, source spins ($\uparrow_s$ ... More

Cloaking in-plane elastic waves with swiss rollsAug 07 2019We propose a design of cylindrical elastic cloak for coupled in-plane shear waves consisting of concentric layers of sub-wavelength resonant stress-free inclusions shaped as swiss-rolls. The scaling factor between inclusions' sizes is according to Pendry's ... More

Reconfigurable Liquid Crystal Reflectarray Metasurface for THz CommunicationsAug 07 2019We present computational studies on a proposed 20 by 20 elements electronically reconfigurable liquid crystal (LC) based binary phase reflectarray metasurface, operational at 108 GHz. LC was modelled after Mer's GT3-23001, and full wave simulations have ... More

A distributed active subspace method for scalable surrogate modeling of function valued outputsAug 07 2019We present a distributed active subspace method for training surrogate models of complex physical processes with high-dimensional inputs and function valued outputs. Specifically, we represent the model output with a truncated Karhunen-Lo\`eve (KL) expansion, ... More

A distributed active subspace method for scalable surrogate modeling of function valued outputsAug 07 2019Aug 08 2019We present a distributed active subspace method for training surrogate models of complex physical processes with high-dimensional inputs and function valued outputs. Specifically, we represent the model output with a truncated Karhunen-Lo\`eve (KL) expansion, ... More

Finite-difference time-domain simulation of strong-field ionization: Perfectly matched layer approachAug 07 2019A Finite-Difference Time-Domain (FDTD) scheme with Perfectly Matched Layers (PMLs) is considered for solving the time-dependent Schr\"{o}dinger equation, and simulate the ionization of an electron initially bound to a one-dimensional $\delta$-potential, ... More

Fully numerical calculations on atoms with fractional occupations. Range-separated exchange functionalsAug 07 2019A recently developed finite element approach for fully numerical atomic structure calculations [S. Lehtola, Int. J. Quantum Chem. e25945 (2019)] is extended to the treatment of atoms with spherically symmetric densities via fractional occupations. Specialized ... More