Visible light exposure of galaxy cluster Abell 2744 from NASA/ESA Hubble Space Telescope and ESO's Very Large Telescope, X-ray data from NASA's Chandra X-ray Observatory & math reconstruction of dark matter location. D. Coe & J. Merten/ESO/NASA/ESA/CXC

Physics Theory Seminar with Robert Wexler on Surface Phase Diagrams from Nested Sampling

Robert Wexler (Hosted by Nussinov) from the Department of Chemistry, Washington University in Saint Louis, will be presenting the seminar "Surface Phase Diagrams from Nested Sampling"

Atomic-scale modeling of surface phase equilibria at finite temperatures has always been challenging due to the complexity of surface configurational space and, therefore, the difficulty in computing the free energy of surfaces. In this proof-of-concept work, we predict coverage-temperature surface phase diagrams and identify phase transitions of adsorbates on both flat and stepped facets of the face-centered cubic Lennard-Jones solid. These phase transitions typically feature an enthalpy-driven condensation at higher temperatures and an entropy-driven reordering process at lower temperatures. We capture both energetic and entropic (including translational, rotational, anharmonic vibrational, and configurational) contributions to the surface phase transitions with nested sampling. Overall, we demonstrate the ability and potential of nested sampling for predicting the structure of hard-to-measure in situ surfaces, e.g., that govern the activity and selectivity of heterogeneous catalysts.