Li2B12Si2 : The First Ternary Compound in the System Li/B/Si: Synthesis, Crystal Structure, Hardness, Spectroscopic Investigations, and Electronic Structure

作者: Natascha Vojteer , Melanie Schroeder , Caroline Röhr , Harald Hillebrecht

DOI: 10.1002/CHEM.200701949

关键词: Electronic structureNetwork covalent bondingChemistryBand gapOrthorhombic crystal systemTernary compoundKnoop hardness testRaman spectroscopyCrystallographyCrystal structure

摘要: We present the synthesis, crystal structure, hardness, IR/Raman and UV/Vis spectra, FP-LAPW calculations of electronic structure Li(2)B(12)Si(2), first ternary compound in system Li/B/Si. Yellow, transparent single crystals were synthesized from elements tin as solvent at 1500 degrees C h-BN crucibles arc-welded Ta ampoules. Li(2)B(12)Si(2) crystallizes orthorhombic space group Cmce (no. 64) with a=6.1060(6), b=10.9794(14), c=8.4050(8) A, Z=4. The is characterized by a covalent network B(12) icosahedra connected Si atoms Li located interstitial spaces. closely related to that MgB(12)Si(2) fulfils electron-counting rules Wade Longuet-Higgins. Measurements Vickers (H(V)=20.3 GPa) Knoop microhardness (H(K)=20.4 revealed hard material. band gap was determined experimentally calculated theoretical means. spectra 2.27 eV, which value 2.1 eV agrees well. IR Raman show expected oscillations icosahedral networks. Theoretical investigations bonding this carried out method. results confirm applicability simple enable some structural specialties be explained more detail.

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