INOR 290 |
| The synthesis, crystal structure and a chemical bonding description of a new metastable binary barium silicide, Ba16Si13, will be presented. The new binary phase in the Ba-Si system was synthesized from high-temperature reactions (820-855 ºC) of the pure elements, within Ta tube containers. The compound crystallizes with a complex tetragonal unit cell (space group P4/n 21/m 2/m (No. 129); a = 12.0660(4)Å; c = 27.383(1)Å; Z = 4) that features a variety of Si anion species: isolated Si atoms ([Si]4-), Si2 dimers ([Si2]6-), Si4 squares ([Si4]8-), and Si6 planar rings ([Si6]12-). However, contrary to the formal Zintl assignment, band structure calculations show the Si2 rings and Si4 squares exhibit π-conjugation and σ-bonding, as [Si6]10- and [Si4]6- respectively, analogous to unsaturated aromatic hydrocarbon systems. In addition, the higher charged (per atom) species (Si4- and Si26-) exhibit a predominance of strong Ba-Si bonds that optimize the chemical bonding. The results of the band structure calculations indicate metallic conductivity. |
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Solid State Chemistry
7:00 PM-10:00 PM, Sunday, August 19, 2007 BCEC -- Exhibit Hall - B2, Poster
Division of Inorganic Chemistry |