Comparative modelling of chemical ordering in palladium-iridium nanoalloys

Abstract

Chemical ordering in "magic-number" palladium-iridium nanoalloys has been studied by means of density functional theory (DFT) computations, and compared to those obtained by the Free Energy Concentration Expansion Method (FCEM) using derived coordination dependent bond energy variations (CBEV), and by the Birmingham Cluster Genetic Algorithm using the Gupta potential. Several compositions have been studied for 38- and 79-atom particles as well as the site preference for a single Ir dopant atom in the 201-atom truncated octahedron (TO). The 79- and 38-atom nanoalloy homotops predicted for the TO by the FCEM/CBEV are shown to be, respectively, the global minima and competitive low energy minima. Significant reordering of minima predicted by the Gupta potential is seen after reoptimisation at the DFT level.

DFT study of the structure, chemical ordering and molecular adsorption of Pd–Ir nanoalloys

“…To compare the properties of alloyed clusters and pure clusters, the d-band center is calculated as: 28,41…”

“…23,24 Pd-Ir nanoalloys are often used as catalysts in the preferential oxidation of CO (PROX). 8,10 The Pd-Ir system has rarely been studied computationally, [25][26][27][28][29] and relatively few catalytic studies have been devoted to Pd-Ir nanoalloys. 9,27,30 In this study, the structure and chemical ordering of bare and CO-adsorbed Pd-Ir nanoalloys have been investigated theoretically by using density functional theory (DFT).…”

A density functional study on the reactivity enhancement induced by gold in IrAu nanoalloys

“…The construction of Ir clusters was guided by the combination of building blocks found for Ir clusters that had between 10 and 20 atoms. 27,30,33 Evidence of these building blocks has also been observed in STEM (Scanning Transmission Electron Microscopy) images. 24,34 IrAu NAs were constructed as cubic structures and also guided by the structure of the most stable Ir clusters.…”

How the hydrogen sorption properties of palladium are modified through interaction with iridium

“…In this context, until now, the most advanced work on PdIr is based on DFT calculations performed on small clusters containing 13 to 79 atoms. Both structural and adsorption studies have been carried out, the latter involving benzene, hydrogen and carbon monoxide molecules 10,12,13 . Although these studies show some nanosize effects both on the atomic structure and the reactivity, larger size nanoparticles are hardly handleable within first-principle calculations.…”