STRUCTURAL RELATIONS IN THE FAMILY OF NONMETALLIC FILLED BETA-MANGANESE PHASES - THE NEW MEMBERS AGA(6)TE(10) (A SN, PB) AND PBIN6TE10

Nonmetallic filled beta-manganese phases form a new class of solids wi th a wide spaced (''eutactical'') partial structure of nonmetal atoms (Te, I), which is topologically equivalent to the arrangement of manga nese atoms in cubic beta-Mn (a = 6.315 Angstrom, P4(1)32, Z = 20), a m anganese polymorph crystallizing in a tetrahedrally close packed struc ture. Different fractions of the 100 tetrahedral and 4 metaprismatic h oles per unit cell of the beta-Mn like arrangement of nonmetal atoms a re occupied by metal atoms or pairs of covalently bonded metal atoms, leading to the different chemical compositions M(7)Te(10), AM(6)Te(10) , Ag2Ga6Te10, RbX(4)I(5) (M: Al, Ga, In; A: Ca, Pb, Sn; X: Ag, Cu;). B asic structural properties and structural relations between the member s of this new family of solids are discussed. In addition we present s tructural data for three new members of the family of filled beta-Mn p hases: SnCa6Te10 (single crystal data: a = 10.203 Angstrom, alpha = 89 .94 degrees, space group R32, Z = 2) PbIn6Te10 (single crystal data: a = 10.619 Angstrom, R32, Z = 2) and PbGa6Te10 (powder data: a = 10.237 Angstrom, alpha = 89.93 degrees, R32, Z = 2).