Modeling energy conversion dynamics at interfaces

Dr. Jörg Meyer

Chemical reactions go hand-in-hand with an energy exchange with the environment in which they take place. Surfaces offer a variety of energy dissipation channels, constituted by the nuclear and electronic degrees of freedom of the atoms at the interface. Aiming at an improved future harvesting of energy, we are developing and applying computational methods to obtain a better fundamental understanding of interfacial energy conversion dynamics.

Quantum mechanical (QM) modeling is required in order to accurately account for bond breaking and making during chemical reactions. Density-functional theory (DFT) in particular has proven to be a very successful tool in that respect, in particular when it comes to the description of metallic surfaces. Still, its computational effort limits the time and length scale that can be modeled in dynamical simulations. Already a simple back-on-the-envelope calculation using the speed of sound allows to estimate that these limitations can affect the description of heat transport in the solid via vibrations of the lattice (phonons). With our recently developed new “QM/Me” embedding scheme [2], which links QM- modeling to molecular mechanics (MM) for metallic systems, we can overcome such limitations.

Since there is no energetic gap between the valence band (VB) and the conduction band (CB) in metallic systems, chemical dynamics at the interface can easily excite electrons. This leads to the violation of one of the most fundamental approximations in theoretical modeling, the Born-Oppenheimer approximation, and provides another elementary channel for energy dissipation. Characterizing and quantifying these electron- hole-pair excitations [4] and including their effect on dynamics at an interface [1] poses a formidable theoretical challenge, which we are facing by the development and application of new computational methods.

  1. Wijzenbroek, M., D. Helstone, J. Meyer, G.-J. Kroes, "Dynamics of H2 dissociation on the close-packed (111) surface of the noblest metal: H2 + Au(111)", The Journal of Chemical Physics, vol. 145, issue 14, pp. 144701, 10/2016. DOI: 10.1063/1.4964486
  2. Doblhoff-Dier, K., J. Meyer, P.E. Hoggan, G.-J. Kroes, L.K. Wagner, "Diffusion Monte Carlo for Accurate Dissociation Energies of 3d Transition Metal Containing Molecules", Journal of Chemical Theory and Computation, vol. 12, issue 6, pp. 2583 - 2597, 06/2016. DOI: 10.1021/acs.jctc.6b00160
  3. Rittmeyer, S.P., J. Meyer, I.J. Juaristi, K. Reuter, "Electronic Friction-Based Vibrational Lifetimes of Molecular Adsorbates: Beyond the Independent-Atom Approximation", Physical Review Letters, vol. 115, issue 4, 7/2015. DOI: 10.1103/PhysRevLett.115.046102
  4. Goikoetxea, I., J. Meyer, J.  I. Juaristi, M. Alducin, K. Reuter, "Role of Physisorption States in Molecular Scattering: A Semilocal Density-Functional Theory Study on", Physical Review Letters, vol. 112, issue 15, 4/2014. DOI: 10.1103/PhysRevLett.112.156101
  5. Meyer, J., K. Reuter, "Modeling Heat Dissipation at the Nanoscale: An Embedding Approach for Chemical Reaction Dynamics on Metal Surfaces", Angewandte Chemie International Edition, vol. 53, issue 18, pp. 4721 - 4724, 04/2014. DOI: 10.1002/anie.201400066

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