Abstract: | New Alkalioxoarsenates (V). On Rb2Li[AsO4] and Cs2Li[AsO4] By heating of well-grounded mixtures of the binary oxides (A2O, Li2O2, and As2O3; A : Li : As = 2 : 1 : 1; Ni-tube, 550°C, 21 d; A = Rb, Cs) colourless single crystals of Rb2Li[AsO4] and Cs2Li[AsO4] were obtained for the first time. These new orthoarsenates(V) crystalize orthorhombic (space group C mc21? C, No. 36) with Z = 4. As expected they are isotypic with the according orthovanadates(V) [2] A2Li[VO4], A = Rb, Cs. The lattice constants of Rb2Li[AsO4]: a = 582.1(4) pm, b = 1171.1(7) pm, c = 792.4(5) pm and Cs2Li[AsO4]: a = 596.4(2) pm, b = 1223.4(2) pm, c = 819.7(3) pm were taken from Guinier-Simon powder data. The structure was determined by four-circle-diffractometer data [Siemens AED II, MoKα , 6290 I0 (hkl), R = 3.5%, Rw = 3.2% to Rb2Li[AsO4]; 3518 I0 (hkl), R = 2.8%, Rw = 2.6% to Cs2Li[AsO4]; parameters see text]. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, these calculated via Mean Fictive Ionic Radii, MEFIR, as well as charge distribution CHARDI are calculated and discussed. |