Web Release Date: March 15,
First-Principles Modeling of Unpassivated and Surfactant-Passivated Bulk Facets of Wurtzite CdSe: A Model System for Studying the Anisotropic Growth of CdSe Nanocrystals
and
National Nanotechnology Lab of INFM, Via Arnesano Km 5, 73100 Lecce, Italy, Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and Department of Chemistry, University of California at Berkeley and Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, 94720
Received: November 30, 2004
In Final Form: February 10, 2005
Abstract:
Equilibrium geometries, surface energies, and surfactant binding energies are calculated for selected bulk
facets of wurtzite CdSe with a first-principles approach. Passivation of the surface Cd atoms with alkyl
phosphonic acids or amines lowers the surface energy of all facets, except for the polar 000
facet. On the
nonpolar facets, the most stable configuration corresponds to full coverage of surface Cd atoms with surfactants,
while on the polar 0001 facet it corresponds only to a partial coverage. In addition, the passivated surface
energies of the nonpolar facets are in general lower than the passivated polar 0001 facet. Therefore, the polar
facets are less stable and less efficiently passivated than the nonpolar facets, and this can rationalize the
observed anisotropic growth mechanism of wurtzite nanocrystals in the presence of suitable surfactants.
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