On the thermodynamic stability of PdO surfaces

TL;DR

This study uses density-functional theory and atomistic thermodynamics to analyze the stability of all 1x1 low-index surfaces of PdO, revealing the PdO(100) surface as most stable across various oxygen conditions.

Contribution

It provides a comprehensive first-principles thermodynamic analysis of PdO surface terminations, highlighting the stability of the PdO(100) surface in different environments.

Findings

PdO(100) surface is most stable across conditions

Polar PdO-terminated PdO(100) dominates the equilibrium shape

Surface reconstructions may alter real crystal morphology

Abstract

As a first step towards understanding the morphology of PdO crystals we performed a systematic full-potential density-functional theory study of all possible 1 x 1 terminations of the low-index surfaces of tetragonal PdO. Applying the concept of first-principles atomistic thermodynamics we analyze the composition, structure and stability of these PdO orientations in equilibrium with an arbitrary oxygen environment. Within the studied subset of 1 x 1 geometries the polar PdO-terminated PdO(100) orientation turns out to be surprisingly stable over the whole range of experimentally accessible gas phase conditions. Setting up a constrained Wulff construction within the compiled data set, this PdO(100)-PdO facet correspondingly dominates the obtained polyhedron by far. The real PdO crystallite shape will however likely be affected by surface reconstructions, which are not covered by the present study.