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    The DOE Science News Source is a Newswise initiative to promote research news from the Office of Science of the DOE to the public and news media.
    • 2014-12-23 03:00:00
    • Article ID: 627801

    Breakthrough in Predictions of Pressure-Dependent Combustion Chemical Reactions

    LIVERMORE, Calif. — Researchers at Sandia and Argonne national laboratories have demonstrated, for the first time, a method to successfully predict pressure-dependent chemical reaction rates. It’s an important breakthrough in combustion and atmospheric chemistry that is expected to benefit auto and engine manufacturers, oil and gas utilities and other industries that employ combustion models.

    A paper describing the work, performed by researchers at Sandia’s Combustion Research Facility and Argonne’s Chemical Sciences and Engineering Division, is featured in the Dec. 5 edition of Science.

    Combustion scientists have worked for years to better understand the thousands of chemical reactions that take place during the combustion process, said Sandia’s Ahren Jasper, the study’s lead author.

    As scientists determine and understand the speeds and outcomes of more and more of these reactions, he said, they can use models to more fully characterize what’s occurring inside an engine, and thus better predict combustion efficiency and the emissions formed during combustion.

    A more detailed, fundamental understanding of the chemistry of combustion, in turn, may lead to cleaner and more efficient strategies in automotive vehicle and fuel design.

    Argonne chemist Stephen Klippenstein, a corresponding author of the study, said this method should aid development of global models for all gas phase chemical environments, including the Earth’s atmosphere. Better models will improve understanding of climate change and boost efforts to address it.

    Pressure-dependent reactions historically a vexing problem

    Many of the key steps underlying gas-phase combustion involve elementary chemical reactions that are strongly pressure-dependent, and researchers who develop combustion models require detailed descriptions of these reactions.

    While significant progress has been made over the years in understanding combustion chemistry, the outcome and rates of pressure-dependent chemical reactions — those that depend on the pressure of the gas in the engine — have been very difficult to predict. These reactions depend on the pressure because the redistribution of energy and angular momentum that occurs when the reacting molecules collide with other gas molecules changes the speed and outcome of the reactions.

    Previous qualitative research focused on how various molecular properties influence energy transfer rates, but no accurate method could make a priori predictions of the rate constants, that is, predictions based on theoretical deduction, not observation.

    “We’ve desperately needed the ability to compute and calculate precisely how chemical reactions depend on temperature and pressure, and now we have that,” said Jasper.

    Focus on energy transfer leads to technical solution

    The team focused on modeling the collisions of molecules in atomistic detail and characterizing the transfer of energy and angular momentum that takes place as a result of those collisions.

    “We succeeded by using more accurate models for describing the interaction of the colliding species and by focusing on only those aspects of energy transfer that are most relevant in determining the reaction rate,” Jasper said. This allowed the researchers to develop a detailed description of collision outcomes.

    Jasper and his colleagues then were able to obtain that collision outcome information using direct “classical trajectories” that explicitly describe the motion of the atoms in the molecules, and to use this information in calculating chemical reaction rates.

    A key step, Jasper said, was the development of a model for the collisional energy and angular momentum transfer function that reproduced detailed features predicted by the trajectories and was simple enough to be used in practical reaction rate calculations.

    “Finding a way to accurately compute and represent the energy and angular momentum transfer from these vibrationally-excited molecules proved to be the final piece needed to solve the problem,” said Jasper.

    “The overall theoretical model is rather complex, involving many separate unrelated calculations, and it is remarkable how accurately one can now treat all aspects of the problem in developing such completely a priori predictions,” Klippenstein said.

    The study was also co-authored by Klippenstein and Larry Harding, both distinguished fellows at Argonne, and the influential combustion modeler Jim Miller, a former Sandia staff member now at Argonne. The work continues the team’s longstanding development of master equation and elementary reaction rate theories.

    “This effort was a true collaboration with both labs playing key roles in the intellectual foundations of the work as well as in the actual computations,” Klippenstein noted. “The combined expertise in energy transfer calculations and in reaction rate theories was central to the success of the project.”

    Miller added: “A close but loose-knit working group was developed with these combustion modeling experts over the years, and we’ve developed excellent professional relationships that have led to this technical achievement.”

    The work was supported by the Department of Energy’s Office of Science.

    ________________________________________

    Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corp., for the U.S. Department of Energy’s National Nuclear Security Administration. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major R&D responsibilities in national security, energy and environmental technologies and economic competitiveness.

    Sandia news media contact: Mike Janes, mejanes@sandia.gov, (925) 294-2447

    Argonne media relations contact: Jared Sagoff, jsagoff@anl.gov, (630) 252-5549

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    From the Cosmos to Fusion Plasmas, PPPL Presents Findings at Global APS Gathering

    Invited Princeton Plasma Physics Laboratory talks at 60th American Physical Society-Department of Plasma Physics annual meeting.

    Scientists Bring Polymers Into Atomic-Scale Focus

    A Berkeley Lab-led research has adapted a powerful electron-based imaging technique to obtain a first-of-its-kind image of atomic-scale structure in a synthetic polymer. The research could ultimately inform polymer fabrication methods and lead to new designs for materials and devices that incorporate polymers.

    Probing Water's "No-Man's Land" Temperature Region

    Measuring the physical properties of water at previously unexplored temperatures offers insights into one of the world's essential liquids.

    Novel Soil Bacteria with Unusual Genes Synthesize Unique Antibiotic Precursors

    A large-scale soil project uncovered genetic information from bacteria with the capacity to make specialized molecules that could lead to new pharmaceuticals.

    RTI International to Perform Large-Scale Tests of Its Innovative Carbon Capture Technology for Cleaner, Less Costly Power

    RTI International announced today its participation in a 2-1/2 year collaborative project to advance its non-aqueous solvent (NAS)-based CO2 capture technology for post-combustion CO2 capture at coal-fired power plants

    Unlocking the Secrets of Metal-Insulator Transitions

    Using an x-ray technique available at the National Synchrotron Light Source II (NSLS-II), scientists found that the metal-insulator transition in the correlated material magnetite is a two-step process. The researchers from the University of California Davis published their paper in the journal Physical Review Letters.

    Scientists find great diversity, novel molecules in microbiome of tree roots

    Researchers with the Department of Energy's Oak Ridge National Laboratory have discovered that communities of microbes living near tree roots are ten times more diverse than the human microbiome and produce a cornucopia of novel molecules that could be useful as antibiotics and anti-cancer drugs.

    Broad genome analysis shows yeasts evolving by subtraction

    An unprecedented comparison of hundreds of species of yeasts has helped geneticists brew up an expansive picture of their evolution over the last hundreds of millions of years, including an analysis of the way they evolved individual appetites for particular food sources that may be a boon to biofuels research.

    Scientists shuffle the deck to create materials with new quantum behaviors

    Layered transition metal dichalcogenides or TMDCs--materials composed of metal nanolayers sandwiched between two other layers of chalcogens-- have become extremely attractive to the research community due to their ability to exfoliate into 2D single layers.

    Researchers create most complete high-res atomic movie of photosynthesis to date

    Despite its role in shaping life as we know it, many aspects of photosynthesis remain a mystery. An international collaboration between scientists at SLAC National Accelerator Laboratory, Lawrence Berkeley National Laboratory and several other institutions is working to change that. The researchers used SLAC's Linac Coherent Light Source (LCLS) X-ray laser to capture the most complete and highest resolution picture to date of Photosystem II, a key protein complex in plants, algae and cyanobacteria responsible for splitting water and producing the oxygen we breathe.


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    Sierra Reaches Higher Altitudes, Takes Number Two Spot on List of Fastest Supercomputers

    Sierra, Lawrence Livermore National Laboratory's newest supercomputer, rose to second place on the list of the world's fastest computing systems, TOP500 List representatives announced Monday at the International Conference for High Performance Computing, Networking, Storage and Analysis conference (SC18) in Dallas.

    Green energy: Wind energy agreement will provide savings, 50 percent of electricity needs for Kansas State University Manhattan campus

    Kansas State University has signed an agreement with Westar Energy to provide approximately 50 percent of the energy needs for the university's main Manhattan campus from a wind farm in Nemaha County and save the university nearly $200,000 annually.

    INCITE grants awarded to 62 computational research projects

    The U.S. Department of Energy announced new projects for 2019 through its Innovative and Novel Computational Impact on Theory and Experiment (INCITE) program.

    Argonne's Raj Kettimuthu Named ACM Distinguished Member

    Argonne computer scientist Raj Kettimuthu recently was named a Distinguished Member of the Association for Computing Machinery for his development of tools to analyze and enhance end-to-end data transfer performance.

    Jefferson Lab-Affiliated Researchers Honored as APS Fellows

    The Department of Energy's Thomas Jefferson National Accelerator Facility now has a few more fellows on campus. The American Physical Society, a professional membership society that works on behalf of the physics community, recently announced its list of 2018 fellowships.

    Jefferson Lab Receives DOE Award for Energy Efficient Upgrade

    On Oct. 23, a team from the Department of Energy's Thomas Jefferson National Accelerator Facility was honored at the 2018 Federal Energy and Water Management Award Ceremony for upgrades made to the lab's data center, ultimately improving its energy efficiency.

    Free Science Events and Educational Opportunities Expected to Draw Thousands

    The Plasma Sciences Expo--planned as the biggest celebration of plasma physics in the country--presents teachers, students and the public with a free opportunity to explore what scientists call "the fourth state of matter."

    Triad National Security Takes the Helm at Los Alamos National Laboratory

    LOS ALAMOS, N.M., November 1, 2018 -- Los Alamos National Laboratory begins operations today under a new management and operating (M&O) contract between Triad National Security, LLC (Triad) and the U.S. Department of Energy's National Nuclear Security Administration (NNSA). The NNSA awarded the M&O contract to Triad on June 8, 2018.

    Texas McCombs Master of Science Programs in Finance, Marketing and Energy Receive STEM Certification

    Several programs within the McCombs School of Business have received STEM designation.

    Brookhaven Lab Launches "PubSci Playback" Podcast

    Brookhaven National Laboratory has launched a podcast based on its live science cafe and conversation series, PubSci. Since 2014, PubSci has been offering the public a chance to see a more casual side of the groundbreaking science happening every day at Brookhaven Lab.


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    Probing Water's "No-Man's Land" Temperature Region

    Measuring the physical properties of water at previously unexplored temperatures offers insights into one of the world's essential liquids.

    Novel Soil Bacteria with Unusual Genes Synthesize Unique Antibiotic Precursors

    A large-scale soil project uncovered genetic information from bacteria with the capacity to make specialized molecules that could lead to new pharmaceuticals.

    Warmer Temperatures Lengthen Growing Season, Increase Plants' Vulnerability to Frost

    Experimental warming treatments show how peatland forests may respond to future environmental change.

    Rising Stars Seek to Learn from the Master: Mother Nature

    A trio of scientists was recognized for their early career successes in uncovering how microbes produce fuel, insights that could change our energy portfolio

    How Plant Cells Decide When to Make Oil

    Signaling mechanism details discovered, potentially leading to strategies to engineer plants that make more bio-oil.

    Cryocooler Cools an Accelerator Cavity

    Researchers demonstrated cryogen-free operation of a superconducting radio-frequency cavity that might ease barriers to its use in societal applications.

    Shining Light on the Separation of Rare Earth Metals

    New studies identify key molecular characteristics to potentially separate rare earth metals cleanly and efficiently with light.

    Placing Atoms for Optimum Catalysts

    Precise positioning of oxygens could help engineer faster, more efficient energy-relevant chemical transformations.

    How to Make Soot and Stardust

    Scientists unlock mystery that could help reduce emissions of fine particles from combustion engines and other sources.

    Breaking the Symmetry Between Fundamental Forces

    Scientists improve our understanding of the relationship between fundamental forces by re-creating the earliest moments of the universe.


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