Dilithium Hexaboride, Li2B6

✍ Scribed by Gunther Mair; Hans Georg von Schnering; Michael Wörle; Reinhard Nesper*

• Book ID: 101306067
• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: German
• Weight: 121 KB
• Volume: 625
• Category: Article
• ISSN: 0372-7874
• DOI: 10.1002/(sici)1521-3749(199907)625:7<1207::aid-zaac1207>3.0.co;2-9

✦ Synopsis

Li 2 B 6 is formed from the elements as transparent red microcrystalline compound (Li : B = 1 : 3; Mo crucible in closed Nb ampoule; 1723 K; 4 h). Single crystals are grown from a lithium silicide melt with large Li excess at 1923 K. Li 2 B 6 is a semiconductor with electron as well as Li + ionic conductivity which dominates above 600 K. Microcrystalline samples react with H 2 O liberating gases and forming a brownish amorphous product, but larger crystals are not very sensitive. ± Li 2 B 6 crystallizes tetragonally in a new tP16 structure type which is a variant of the CaB 6 structure (a = 5.975 A Ê , c = 4.189 A Ê ; Z = 2; space group P4/mbm). The 3 [B 62± ] net of the polymeric octahedro-anion is slightly distorted to give space for the insertion of a (3 2 434) net of the Li + cations in the cavities (d(B±B) endo = 1.766 A Ê ; d(B±B) exo = 1.720 A Ê ; d(Li±B) = 2.363 A Ê ; d(Li±Li) = 3.094 A Ê ). The incomplete occupancy of the Li position (80%) and the electron density at a further position (20%) indicate the mobility of the Li + cations.