Abstract: | New Alkali Oxoarsenates(V): NaLi2[AsO4] — A New Type of Formula [1] . By heating of well ground mixtures of the binary oxides As2O3, Na2O, and Li2O2, molar ratio As:Na:Li = 1.0:1.0:2.0, in a well closed Ni tube (650°C, 21 d) colourless single crystals of NaLi2[AsO4] were obtained for the first time. The new orthoarsenate(V) crystallizes orthorhombic (space group P mn21-C, No. 31) with Z = 2. The structure determination showed that it is isostructural to βII-Li3[VO4] and that means the Li3[PO4]-type. The lattice constants a = 702.9(2) pm, b = 520.5(1) pm, c = 505.4(2) pm were taken from Guinier-Simon powder data. The structure was determined by four-circle diffractometer data [Philips PW 1 100, AgKα , 679 independent out of 2 373 Io(hkl), R = 3.03%, Rw = 2.29%; parameter see text]. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, these calculated via Mean Fictive Ionic Radii, MEFIR, are calculated and discussed. |