Translational dependence of the geometry of metallic mono- and bilayers optimized on semi-ionic supports: the cases of Pd on γ-Al2O3(110), monoclinic ZrO2(001), and rutile TiO2(001)

Abstract

A simplified computational scheme for “deposition” of a metallic (Pd) monolayer on semi-ionic supports is considered. An arbitrary selection of the initial position of the deposited layer relative to the surface of the support cannot provide the best solution for an optimal atom–atom binding. The energy and/or geometry changes were checked relative to a slide of the mono- and bilayers in parallel to the support layer and re-optimization. Two types of possible consequences are shown at the slide length of 1–3 Å for γ-Al₂O₃(110), monoclinic ZrO₂(001) (or m-ZrO₂), and rutile TiO₂(001) (or TiO₂ below). First consequence option: either the Pd monolayer completely collapses after the shift/optimization, or it yields a new geometry (at γ-Al₂O₃(110) and m-ZrO₂) at different steps. Second consequence option: the shift leads to a loss of the Pd stabilization while the ordered monolayer's geometry is retained (at TiO₂ and m-ZrO₂). The extent of such destabilization varies depending on the strength of the interaction with the support. It is thus recommended to verify Pd stabilization energy by sliding/optimizing the monolayer along one or two monolayer directions in order to avoid its energy underestimation. The activity of such monolayers for modelling catalysis is demonstrated using H₂O dissociation in the Pd monolayer/rutile system.