A5003104055- High-pressure geophysics and materials
- High-Velocity Impact and Material Behavior
- Microstructure and mechanical properties
- Energetic Materials and Combustion
- Metal and Thin Film Mechanics
- Ion-surface interactions and analysis
- Diamond and Carbon-based Materials Research
- Laser-Plasma Interactions and Diagnostics
- Advanced Chemical Physics Studies
- Boron and Carbon Nanomaterials Research
- Force Microscopy Techniques and Applications
- COVID-19 epidemiological studies
- Quantum, superfluid, helium dynamics
- Aluminum Alloys Composites Properties
- Adhesion, Friction, and Surface Interactions
- MXene and MAX Phase Materials
- Machine Learning in Materials Science
- Metallurgy and Material Forming
- Parallel Computing and Optimization Techniques
- Combustion and Detonation Processes
- Advanced ceramic materials synthesis
- Distributed and Parallel Computing Systems
- Intermetallics and Advanced Alloy Properties
- nanoparticles nucleation surface interactions
- Molecular Spectroscopy and Structure
Los Alamos National Laboratory
2016-2025
Government of the United States of America
2023
Northwestern University
2017-2022
The University of Texas at El Paso
2007-2022
Michigan State University
2021
Los Alamos Medical Center
2017-2019
Midwestern University
2017
Lawrence Livermore National Laboratory
2004-2013
University of St. Gallen
2013
University of Science and Technology of China
2009
Recent human deaths due to infection by highly pathogenic (H5N1) avian influenza A virus have raised the specter of a devastating pandemic like that 1917-1918, should this evolve become readily transmissible among humans. We introduce and use large-scale stochastic simulation model investigate spread strain through U.S. population 281 million individuals for R(0) (the basic reproductive number) from 1.6 2.4. impact variety levels combinations antiviral agents, vaccines, modified social...
Planning a response to an outbreak of pandemic strain influenza is high public health priority. Three research groups using different individual-based, stochastic simulation models have examined the consequences intervention strategies chosen in consultation with U.S. workers. The first goal simulate effectiveness set potentially feasible strategies. Combinations called targeted layered containment (TLC) antiviral treatment and prophylaxis nonpharmaceutical interventions quarantine,...
▪ Abstract Obtaining a good atomistic description of diffusion dynamics in materials has been daunting task owing to the time-scale limitations molecular method. We discuss promising new methods, derived from transition state theory, for accelerating simulations these infrequent-event processes. These hyperdynamics, parallel replica dynamics, temperature-accelerated and on-the-fly kinetic Monte Carlo, can reach simulation times several orders magnitude longer than direct while retaining full...
Multimillion-atom molecular-dynamics simulations are used to investigate the shock-induced phase transformation of solid iron. Above a critical shock strength, many small close-packed grains nucleate in shock-compressed body-centered cubic crystal growing on picosecond time scale form larger, energetically favored grains. A split two-wave structure is observed immediately above this threshold, with an elastic precursor ahead lagging wave. For even higher strengths, single, overdriven wave...
We report on large-scale nonequilibrium molecular dynamics simulations of shock wave compression in tantalum single crystals. Two new embedded atom method interatomic potentials Ta have been developed and optimized by fitting to experimental density functional theory data. The reproduce the isothermal equation state up 300 GPa. examined nature plastic deformation elastic limits as functions crystal orientation. Shock waves along (100), (110), (111) exhibit elastic-plastic two-wave...
Abstract Designing highly active and bifunctional oxygen reduction reaction (ORR) evolution (OER) catalysts has attracted great interest toward metal–air batteries. Herein, an efficient solution to the search for MXene‐based is proposed by introducing non‐noble metals such as Fe/Co/Ni at surfaces. These results indicate that ultrahigh activities in Ni1/Ni2‐ Fe1/Ni2‐modified double‐atom (DACs) ORR/OER are better than those of well‐known unifunctional with low overpotentials, Pt(111) ORR IrO 2...
Two-dimensional (2D) materials have attracted considerable interest due to their remarkable properties and potential applications for nanoelectronics, electrodes, energy storage devices, among others. However, many well-studied 2D lack appreciable conductivity tunable mechanical strength, limiting in flexible devices. Newly developed MXenes open up the opportunity design novel conductive electronic materials. Here, using density functional theory (DFT), we investigate systematically effects...
In situ x-ray diffraction studies of iron under shock conditions confirm unambiguously a phase change from the bcc (alpha) to hcp (epsilon) structure. Previous identification this transition in shock-loaded has been inferred correlation between shock-wave-profile analyses and static high-pressure measurements. This is intrinsically limited because dynamic loading can markedly affect structural modifications solids. The measurements are consistent with uniaxial collapse along [001] direction...
By multimillion-atom classical molecular dynamics simulations employing an embedded atom method potential, we investigate shock-induced phase transformations in body-centered cubic Fe single crystals caused by shock loading along ${[001]}_{\mathrm{bcc}}$, ${[011]}_{\mathrm{bcc}}$, and ${[111]}_{\mathrm{bcc}}$ directions. Significant dependence of the developing microstructure on crystallographic direction is evident, but see only a weak transition pressures for...
We use multimillion-atom molecular dynamics simulations to study shock wave propagation in fcc crystals. As shown recently, waves along the $〈100〉$ direction form intersecting stacking faults by slippage ${111}$ close-packed planes at sufficiently high strengths. find even more interesting behavior of shocks propagating other low-index directions: for $〈111〉$ case, an elastic precursor separates front from slipped (plastic) region. Shock $〈110〉$ generate a leading solitary train, followed...
We investigate spallation in solid and liquid Cu at high strain rates induced by planar shock loading with classical molecular dynamics. Shock simulations are performed different initial temperatures stresses but similar (ε̇∼1010–1011s−1). The anisotropy spall strength (σsp) is explored for five crystallographic orientations, ⟨100⟩, ⟨110⟩, ⟨111⟩, ⟨114⟩, ⟨123⟩. For liquid, we examine shock- release-induced melts as well premelted Cu. acoustic method deducing σsp ε̇ a reasonable first-order...
The propagation of shock waves through polycrystalline iron is explored by large-scale atomistic simulations. For large enough strengths the passage wave causes body-centered-cubic phase to transform into a close-packed with most structure being isotropic hexagonal-close-packed (hcp) and, depending on strength and grain orientation, some fraction face-centered-cubic (fcc) structure. simulated Hugoniot compared experiments. By calculating extended x-ray absorption fine (EXAFS) directly from...
As noted in Wikipedia, skin the game refers to having ‘incurred risk by being involved achieving a goal’, where ‘ is synecdoche for person involved, and metaphor actions on field of play under discussion’. For exascale applications development US Department Energy Exascale Computing Project, nothing could be more apt, with delivering comprehensive science-based computational that effectively exploit high-performance computing technologies provide breakthrough modelling simulation data...
Accuracy of molecular dynamics simulations depends crucially on the interatomic potential used to generate forces. The gold standard would be first-principles quantum mechanics (QM) calculations, but these become prohibitively expensive at large simulation scales. Machine learning (ML) based potentials aim for faithful emulation QM drastically reduced computational cost. accuracy and robustness an ML is primarily limited by quality diversity training dataset. Using principles active (AL), we...
Subsurface formations are promising for large-scale H2 storage, balancing the energy demand and supply. Wettability is vital in ensuring storage safety, efficiency, capacity, whereas noticeable discrepancies exist literature. This work reconciles these by revealing mechanisms of quartz wettability alteration with surface chemistry pressure using classical molecular dynamics simulation. We find that fully rigid substrate results much lower hydrophilicity than flexible hydroxyl group...
We present an alternative equilibrium molecular dynamics method---the uniaxial constant-stress Hugoniostat---for following the dynamical evolution of condensed matter subjected to shock waves. It is a natural extension recently developed constant-volume Hugoniostat [Maillet et al., Phys. Rev. E 63, 016121 (2001)]. Integral feedback employed reach Hugoniot (final) state process by controlling both normal component stress tensor and internal energy. The finite strain rate imposed on system...
As computational power is increasing, molecular dynamics simulations are becoming more important in materials science, chemistry, physics, and other fields of science. We demonstrate weak strong scaling our classical code SPaSM on Livermore's BlueGene/L architecture containing 131 072 IBM PowerPC440 processors. A maximum 320 billion atoms have been simulated double precision, corresponding to a cubic piece solid copper with an edge length 1.56 μm.
Recent published work has shown that the phase change of shock-compressed iron along [001] direction does transform to $ϵ$ [hexagonal close-packed (hcp)] similar case for static measurements. This article provides an in-depth analysis experiment and nonequilibrium molecular dynamics simulations, using x-ray diffraction in both cases study crystal structure upon transition. Both simulation are consistent with a compression shuffle mechanism responsible from body-centered cubic hcp. Also show...
We present simulations of the dissociation perfect dislocations into extended partial in aluminum, palladium, and nickel using a phase field dislocation dynamics (PFDD) theory that incorporates $\ensuremath{\gamma}$ surface. As expected from theory, show increasing intrinsic stacking fault energy, normalized by product shear modulus Burgers vector, decreases equilibrium width. Significantly, it is also found unstable energy has same effect when held constant. Furthermore, our results...