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Studies of long time scale processes of environmental importance

EMSL Project ID


This proposal addresses two problems of importance to environmental molecular science related by the need to study processes occurring on long times scales. We will use a combination of novel simulation algorithms, analytical theory, and parallel computation as well as experimental measurements to study
? Diffusion of small molecules in glassy materials,
? Growth mechanisms for nanoparticles implicated in biohazard formation.
A simulation of either process requires significant computational resources due to the activation barriers (and related slow dynamics) associated with diffusion in glassy materials and aggregation with reactive growth. Molecular dynamics simulations will be used to study the glassy diffusion, while novel Monte Carlo algorithms will be used to study the aggregation mechanism. The simulation methods will be combined with classical or ab initio (using NWChem or CP2K/Quickstep) potential energy functions to model the intra- and inter-molecular interactions. In addition, experimental work will be used to calibrate and validate the calculations. All simulation methods are designed for massively parallel computer architecture and can be readily modified to run on PNL computers. The team has expertise in the theory, simulation methods, and experimental techniques needed to accomplish the goals of the proposed work.

Growth and reaction of nanoparticles implicated in biohazard formation
One of the most significant environmental issues of the decade is the effect of combustion-generated nanoparticles on human health and the environment. Combustion of solid and liquid fuels form nanoparticles with diameters between a few and several hundred nanometers that contain potentially catalytic metals, organic species, ?elemental carbon?, and minerals. Metals contained in the fuel are vaporized in the flame-zone of the combustor and subsequently either nucleate to form small metal nanoparticles or condense on the surfaces of other nanoparticles in the transition to the post flame (thermal reaction) zone. Target systems for this work are metal-oxide clusters, which we hypothesize to act as catalysts or enhancers for free radical reactions that lead to biohazard formation. Experimental studies will examine the combustion products of small metal oxide nanoparticles and chlorinated and brominated hydrocarbons (CHC and BHC). Growth mechanisms will be studied using novel Monte Carlo methods and either in-house developed effective potentials or direct sampling from first-principles energies (NWChem or CP2K/Quickstep). Reactivities of small metal oxide clusters and CHC?s and BHC?s at different reaction sites on the metal oxide clusters will be studied with standard ab initio methods.

Diffusion of small molecules in viscous materials
This project will study diffusion and aging of small molecules in glassy materials. This is of importance in chemical waste processing. We will use molecular dynamics and tomography to study the diffusion of brominated aromatics in networked and molecular glasses. Computer simulations will help interpret the images and guide the improvement of techniques for image analysis of diffusion processes. Random First Order Transition (RFOT) theory has begun to explain diffusion in glasses. In addition to complementing the tomography, the proposed simulations will explore aspects of RFOT theory (particularly the ?mosaic? picture of glassy dynamics).

Project Details

Project type
Capability Research
Start Date
End Date


Principal Investigator

Randall Hall
Louisiana State University

Team Members

Peter Wolynes
Rice University

Barry Dellinger
Louisiana State University

Leslie Butler
Louisiana State University

Joern Siepmann
University of Minnesota

Bin Chen
Wayne State University

Related Publications

Chen B, X Ren, T Neville, WG Jerome, DW Hoyt, DL Sparks, G Ren, and J Wang. 2009. "Apolipoprotein AI tertiary structures determine stability and phospholipid-binding activity of discoidal high-density lipoprotein particles of different sizes." Protein Science 18(5):921-935. doi:10.1002/pro.101