Richard Dronskowski

SmF4-6 conformation caused by 5d-2p orbital interactions

Abstract Despite having almost equivalent sizes, Sm 2+ and Sr 2+ prefer opposite conformations if coordinated by six F − ligands. Using qualitative molecular orbital calculations, we find that the disparity originates from different amounts of metal d level bonding participation which is greater for Sm 2+ than for Sr 2+ . The influences of ligand repulsion, the participation of the 4 f orbitals of Sm 2+ , and relativistic effects are insignificant. We emphasize the crucial importance of covalency in an essentially ionic system.

First principles model calculations of In +Br − bonding

Abstract In order to elucidate the unusual chemical bonding of the In + Br − combination, the potential energy surfaces of the model complexes InBr87−, In7Br8− and InBr1211− have been studied by means of ab initio all-electron calculations at the STO-3G, STO-3G*, and MP2/STO-3G* levels of theory. In all cases, the highest-symmetry geometrical configurations are local maxima of the energy surfaces. Moreover, the crystal potentials around In + are very soft, allowing small spontaneous distortions as a result of a second-order Jahn-Teller instability. The limits of theoretical accuracy obtainable at the present time are critically evaluated.

A quantum mechanical study on the reactivity and acidity of the LiAlO2-benzoic acid soft chemical reaction

Abstract Solid α-LiAlO 2 exchanges Li + for H + when in contact with molten benzoic acid yet γ-LiAlO 2 does not. Electronic structure calculations on both solid phases show that the reason for Li being substitutable solely in α-LiAlO 2 arises mostly from the difference in Li electrophilicities. Thus, the less acidic Li atom in the α-phase is exchanged against a proton whereas the Li atom in γ-LiAlO 2 is too strong a Lewis acid for the proton to “drive out”. Furthermore, while Li atoms are more weakly bonded within the structural matrix than Al atoms, there is a significantly smaller Li-O binding energy in the α-compared to the γ-phase and the less acidic Li atom (α) is thermodynamically more labile. Finally, one finds a large difference in the energetic behavior upon dislocation of a Li atom from its equilibrium position in the α- and γ-phases. Despite having a high activation barrier, there is a finite kinetic chance for a Li atom to escape from its equilibrium position only in α-LiAlO 2 .