Stability Changes in Iridium Nanoclusters via Monoxide Adsorption: A DFT Study within the van der Waals Corrections.

Small iridium nanoclusters are prominent subnanometric systems for catalysis-related applications, mainly because of a large surface-to-volume ratio, noncoalescence feature, and tunable properties, which are completely influenced by the number of atoms, geometry, and molecular interaction with the chemical environment. Herein, we investigate the interaction between Ir nanoclusters ( = 2-7) and polluting molecules, CO, NO, and SO, using van der Waals D3 corrected density functional theory calculations. Starting from a representative structural set, we determine the growth pattern of the lowest energy unprotected Ir nanoclusters, which is based on open structural motifs, and from the adsorption of a XO (X = C, N, and S) molecule, the preferred high-symmetric adsorption sites were determined, dominated by the onefold top site.

Bare versus protected tetrairidium clusters by density functional theory.

The tetrairidium (Ir4) clusters are subnanometric systems vastly applied in catalysis, especially, because of the higher activity than mononuclear Ir complexes, intrinsic and controllable stability in relation to supports, and non-coalescence properties. The main catalytic properties of nanoclusters (activity and selectivity) are directly associated with their size, shape, and interactions with the environment, whose understanding requires study at the atomistic level. Here, the Ir4 clusters are studied considering the energetic stability for different chemical environments, bare versus protected, using density functional theory calculations within the generalized gradient approximation with van der Waals corrections and spin-orbit coupling, employing the all-electron projected augmented wave method.

Tuning Heterocalixarenes to Improve Their Anion Recognition: A Computational Approach.

We have explored and analyzed the physical factors through which noncovalent interactions in anion sensing based on calixarene-type hosts can be tuned, using dispersion-corrected DFT and Kohn-Sham molecular orbital (KS-MO) theory in conjunction with a canonical energy decomposition analysis (EDA). We find that the host-guest interaction can be enhanced through the introduction of strongly electron-withdrawing groups at particular positions of the arene and triazine units in the host molecule as well as by coordination of a metal complex to the arene and triazine rings. Our analyses reveal that the enhanced anion affinity is caused by increasing the electrostatic potential in the heterocalixarene cavities.