Dependence on CO adsorption of the shapes of multifaceted gold nanoparticles: A density functional theory

We present a computational study for the environment-dependent equilibrium shape of gold nanoparticles. By linking extensive quantum-mechanical calculations, based on density functional theory (DFT), to Wulff constructions, we predict the equilibrium shapes of clean and CO-covered gold nanoparticles. We construct atomistic models of nanoparticles with diameters up to several tenths of a nanometer, inaccessible by direct atomistic simulations. Au nanoparticles smaller than 16.3 nm in diameter have truncated octahedral shape, exposing only (111) and (100) faces. Larger nanoparticles also expose higher-index faces, mostly (332). We study the adsorption of CO on several different Au surfaces, and we use the results to obtain the interface energy between Au and CO at low pressure and temperature. These results are then used to obtain the equilibrium shape of Au nanoparticles in CO gas. In agreement with experimental data, Au nanoparticles in CO are found to be more spherical and more reactive compared to Au nanoparticles in noninteracting environments.