Finite Size Effects in Chemical Bonding: From Small Clusters to Solids
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We address the fundamental question of which size a metallic nano-particle needs to have before its surface chemical properties can be considered to be those of a solid, rather than those of a large molecule. Calculations of adsorption energies for carbon monoxide and oxygen on a series of gold nanoparticles ranging from 13 to 1,415 atoms, or 0.8–3.7 nm, have been made possible by exploiting massively parallel computing on up to 32,768 cores on the Blue Gene/P computer at Argonne National Laboratory. We show that bulk surface properties are obtained for clusters larger than ca. 560 atoms (2.7 nm). Below that critical size, finite-size effects can be observed, and we show those to be related to variations in the local atomic structure augmented by quantum size effects for the smallest clusters.
KeywordsNano-particle Size effects DFT
This research used resources of the Argonne Leadership Computing Facility at Argonne National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under contract DE-AC02-06CH11357. The researchers’ use of Argonne's Center for Nanoscale Materials was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, also under contract No. DE-AC02-06CH11357. Additional support from the Office of Science of the U.S. Department of Energy to the SUNCAT Center for Interface Science and Catalysis at SLAC/Stanford, the NABIIT program under the Danish Strategic Research Council, and from the Lundbeck Foundation to the Center for Atomic-scale Materials Design at DTU is gratefully acknowledged.