Stabilities and Reconstructions of PbTe Crystal Surfaces from Density-Functional Theory

Lead telluride (PbTe) is a well-known functional material with current applications in fields such as nanostructured thermoelectrics. Here, we report comprehensive first-principles simulations for important crystal surfaces of rocksalt-type PbTe. Surface energies have been computed for pristine (001), (011), and (111) surfaces, and a number of relevant (111) surface reconstructions have been explored. Density-functional theory (DFT) was applied at various levels of sophistication and cost, namely, the local density approximation (LDA), the generalized gradient approximation (GGA), and the HSE06 hybrid functional. Overall, PbTe(001) is predicted to be noticeably stable, essentially corroborating previous computational studies that had been performed for this particular termination; here, however, we expand upon these findings and use the computed set of surface-energy data to predict the equilibrium crystallite shape (as reflected by the Wulff construction); the latter is strongly dominated by {001} facets throughout the entire chemical-potential space. For the PbTe(111) surface, atomic reconstructions are investigated, and they emerge as energetically more favorable than either of the two pristine terminations: this in contrast to the lighter homologues GeTe and SnTe. In particular, for PbTe, 2 × 1 and 2 × 2 reconstructions are predicted and assessed in comprehensive surface phase diagrams. The computational results compare favorably to previous experiments including evidence for a 2 × 2 reconstruction of the (111) surface; overall, they may contribute a useful piece of understanding of these important crystal surfaces.