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Chemical Physics

The theoretical Chemical Physics program at Ames Laboratory supports integrated efforts in electronic structure theory and non-equilibrium statistical mechanical & multiscale modeling.  The primary focus is on the development and especially application of methods that enable the study of surface phenomena, heterogeneous catalysis, surface and bulk properties of solid clusters, solvent effects, and mechanisms in organometallic chemistry including solvents and relativistic effects.

Electronic structure theory efforts integrate development of fundamental theory by (expanding the capability for accurate treatment of large or complex systems of interest to DOE), with optimal strategies for computational implementation within GAMESS and NWChem. In particular, this includes development of embedding methods, effective fragment potential approaches, with special interest in liquid-solid interfaces, and a rigorous basis for semi-empirical tight-binding methods, all geared towards applications to various complex condensed phase systems.

The statistical mechanical & multiscale modeling studies often incorporate energetics from electronic structure analyses. A core focus is the modeling of chemisorption and heterogeneous catalysis on metal surfaces. We consider both reactions on extended surfaces (including multiscale studies of spatiotemporal behavior) and in nanoscale catalyst systems (including analysis of fluctuation effects). We also model transport and reaction processes at non-conducting surfaces and in mesoporous systems, and analyze fundamental behavior in general far-from-equilibrium reaction-diffusion systems.

This research is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences through the Ames Laboratory.  The Ames Laboratory is operated for the U.S. Department of Energy by Iowa State University under Contract No. DE-AC02-07CH11358

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  • Gold-coated nanoparticles capture electrons at an unprecedented rate in solution.

  • New research provides insight into design guidelines for the ideal pore width in nanoporous catalytic materials.  Nanoporous materials have long narrow aisles, or pores, around 2 nm in diameter.  In designing these lab-synthesized materials, researchers strive for the greatest amount of surface area to maximize reaction yield while still allowing molecules to pass each other.  Within a single pore molecules have to squeeze past each other, like shoppers in a crowded supermarket aisle.

  • A new series of catalysts is able to selectively make “left-handed” or “right-handed” nitrogen-containing compounds known as amines. Left-handed and right-handed molecules contain the same components, but are mirror images of each other.

  • A new theory shows that reactivity at catalytic sites inside narrow pores is controlled by how molecules move at the pore openings. Like cars approaching a single lane tunnel from which other cars are emerging, the movement of molecules depends on their distance into the pore; near the ends of the pores, exchange is rapid compared to further into the pores. Dynamics at the openings of these pores controls the penetration of reactants and thus overall conversion to products.

  • Researchers can now analyze how reactions proceed inside porous nanoparticles where the molecules are in such narrow channels that they cannot pass each other. Catalysis within these confined conditions is significantly impacted by restricted transport. Typical pore diameters are in the range of 2 - 10 nm, and with catalyst molecules attached inside them, the pore diameter can be reduced below 2 nm. Traditional computational tools do not capture the evolution of concentrations inside pores so narrow that reactants and products cannot pass each other.