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Stabilities and Reconstructions of Clean PbS and PbSe Surfaces: DFT Results and the Role of Dispersion Forces

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journal contribution
posted on 12.04.2016, 00:00 by Volker L. Deringer, Richard Dronskowski
Lead sulfide (PbS) and lead selenide (PbSe) are functional materials with manifold applications. In particular, nanocrystals and other nanostructures of PbS and PbSe are of mounting interest, which calls for a thorough understanding of the underlying crystal surfaces. Here, we present a comprehensive density-functional theory (DFT) survey of structures and stabilities for the (001), (011), and (111) surfaces of rocksalt-type PbS and PbSe. A representative set of possible reconstructions is explored for the polar (111) surfaces, allowing us to suggest both 2 × 1 and “octopolar” 2 × 2 motifs as favorable options; this agrees with previous experiments and could guide future ones. With regard to methodology, we address the role of dispersion interactions for studying PbS and PbSe surfaces: interestingly, the prediction of (001) surface energies depends crucially on the use of dispersion corrections to DFT, and the latter directly influences the computed equilibrium shapes (Wulff constructions). This study may serve as a starting point for future explorations of surfaces and nanocrystals of PbS, PbSe, and chemically related chalcogenide materials.