On lithovanadates: Rb2[LiVO4] and Cs2[LiVO4]

By heating of well ground mixtures of the binary oxides [A2O, Li2O, V2O5, A:Li:V = 2.2:1.1:1.0 ( A = Rb, Cs); Ni-tube, 750 0C, 25 d] we obtained Rb2[LiVO4] and Cs2[LiVO4] colourless, orthorhombic single crystals. We found a new type of 'Lithovanadate'-structure: space group Cmc21; a = 587.9(1), b = 1170.1(1), c = 793.3(1) pm, Z = 4 (A = Rb) bzw. a = 610.5(1), b = 1222.6(3), c = 815.5(2) pm, Z = 4 (A = Cs). The structure was determined by four-circle diffractometer data [MoKα-bar-radiation: 997 from 1157 I0(hkl), R = 7.75%, Rw = 5.54% (A = Rb); 686 from 686 I0(hkl), R = 6.97%, Rw = 4.20% (A = Cs)] parameters. The Madelung part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, have been calculated. (author)