Ein „Lithosilicat”︁ mit Kolumnareinheiten: RbLi5{Li[SiO4]}2

A “Lithosilicate” with Columnar Units: RbLi₅{LiSiO₄]}₂ In order to prepare RbLi₃SiO₄] single crystals of RbLi₅{LiSiO₄]}₂ have been obtained for the first time by heating of a well ground mixture of the binary oxides RbO_0.68, LiO_0.5 and SiO₂ Rb:Li:Si = 1.1:3.0:1.0; 600°C; 21 d] in tightly closed Ni tubes. The new “lithosilicate” crystallizes monoclinic (space group C2/m with a = 1563.1(2) pm, b = 635.4(1) pm, c = 776.3(1) pm, β = 90.53(1)°, Guinier-Simon powder data). The crystal structure was determined by four-cycle diffractometer data Philips PW 1100, 1237 from 1609 I_o(hkl), Z = 4, R = 9.2%, R_w = 8.3%], parameters see text. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, have been calculated.