Ba3SiI2, a double salt of barium iodide and the zintl phase Ba2Si

Reacting Ba2X (X = Si, Ge) with a melt of BaI2, new compounds of the compos ition Ba3I2X were found. These are the simplest representatives of double s alts between Zintl phases and halides. The isotypic structures were refined by single-crystal X-ray data (Fddd, a = 10.057(2), b = 14.064(3), c: 29.52 6(4) Angstrom, R/R-w, = 0.04/0.07 for X= Si, and a = 10.064(2), b = 14,082( 2), c = 29.605(4)Angstrom, R/R-w = 0.03/0.07 for X=Ge), Magnetic measuremen ts show Ba3I2Si to be diamagnetic with a mol susceptibility of 7.7x 10(-5) cm(3)/mol. This is in accordance with conductivity measurements and LMTO ba nd structure calculations which show a semiconducting behavior with an elec tronic band gap of about 0.4 eV. (C) 2000 Academic Press.