An ab initio study of adsorption related properties of diatomic molecules in zeolites

METAL ION-LIGAND INTERACTION: HSAB PRINCIPLE VERSUS NBO AND AIM VIEW POINTS

Ab initio calculations were performed to study the applicability and reliability of the semi quantitative model based on the local hard-soft acid-base principle in studying the interaction of metal ions with ligands. The particular attention is devoted to the interaction of CO , CN - and SCN - as the base with some hard metal ions ( Li +, Na +, K +) and some soft metal ions ( Pd +2, Ag +2, Cd +2) as acids. The interaction energies were calculated using the HSAB principle and compared with the values obtained by the conventional MP2 method. The results show that the HSAB principle does not work in many cases and it fails to predict correct values for interaction energies. The AIM and NBO analyses were also performed to characterize the nature of the metal ion-ligand interaction. It is found that the charge transfers have great significance in the interaction of metal ions with ligands.

DFT Study of Oxygen Adsorption on Modified Nanostructured Gold Pyramids

Periodic DFT calculations are used to predict and investigate the adsorption behavior of molecular oxygen on Au, Au/Pt, and Pt surfaces. To obtain an array of pyramids containing surface atoms with the lowest possible coordination number, a nano-modified surface consisting of a symmetrically "modified" (100) surface was used. The effect of atom substitution (organized alloying) is investigated. The adsorption of molecular oxygen on a pure gold pyramid is exothermic by 0.77 eV for the end-on adsorption mode. In the case of a pure platinum pyramid, the end-on adsorption mode was found to dissociate; however, a side-on geometry was encountered with an energy of adsorption of 2.3 eV. This value is in line with the fact that the adsorption energy of small molecules does not vary much on Pt surfaces with different indices. Additionally, some geometrically related trends of the surface deformation in relation to its composition and after adsorption of molecular oxygen are highlighted.