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Structures, Thermochemical Properties, and Bonding of Mixed Alkaline-Earth-Metal Silicon Trimers Si3M+/0/– with M = Be, Mg, Ca

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journal contribution
posted on 18.06.2015, 00:00 by Tran Dieu Hang, Huynh Minh Hung, Huyen Thi Nguyen, Minh Tho Nguyen
The ground state geometries, electronic structures, and thermochemical properties of binary alkaline-earth-metal silicon clusters Si3M with M = Be, Mg, Ca in neutral, cationic, and anionic states were investigated using quantum chemical computations. Lowest-lying isomers of the clusters were determined on the basis of the composite G4 energies. Along with total atomization energies, thermochemical parameters were determined for the first time by means of the G4 and coupled-cluster theory with complete basis set CCSD­(T)/CBS approaches. The most favored equilibrium formation sequences for Si3M clusters emerge as follows: all Si3M+/0/– clusters are formed by attaching the M atom into the corresponding cation, neutral and anion silicon trimer Si3+/0/–, except for the Si3Mg+ and Si3Ca+ where the metal cations are bound to the neutral Si3. The resulting mixed tetramers exhibit geometrical and electronic features similar to those of the pure silicon tetramer Si4+/0/–. Electron localization function (ELF) and ring current analyses point out that the σ-aromatic character of silicon tetramer remains unchanged upon substituting one Si atom by one alkaline-earth-metal atom.