SYNTHESIS, STRUCTURE, AND PROPERTIES OF BAGE2 - A STUDY OF TETRAHEDRAL CLUSTER PACKING AND OTHER 3-CONNECTED NETS IN ZINTL PHASES

BaGe2 crystallizes in the BaSi2 structure type; space group Pnma (No. 62); a = 9.078(3) Angstrom, b = 6.829(2) Angstrom, c = 11.653(3) Angst rom; Z = 8; R = 0.022; R-w = 0.025 (I > 3 sigma(I)) for 542 reflection s with 2 theta(max) = 50 degrees measured on a single-crystal diffract ometer, Magnetic susceptibility measurements confirm its closed shell behavior (diamagnetic), and electrical resistivity measurements place a lower bound on its room temperature resistivity at ca, 1 m Ohm . cm. Lattice energy calculations rationalize the observed packing arrangem ent of [Ge-4](4-) tetrahedra and Ba2+ cations, while extended Huckel c alculations are utilized to compare the electronic structures of vario us three-connected nets common to Zintl ions with five valence electro ns per atom. (C) 1997 Academic Press.