Two new variants of the NaCl type of structure: on Li4MoO5 and Li4WO5

For the first time in form on colourless, transparent single crystals of Li4MoO5 [annealed mixtures of Li2O and MoO3, Li:Mo = 4.2:1, Ni-cylinder, 950 0C, 28 d] as well as Li4WO5 [annealed mixtures of Li2O and WO3, Li:W = 4.4:1, Au-tube, 950 0C, 28 d, slowly cooling] have been prepared. Single crystal data show isotypic oxides of the Li4TeO5-type, a deformed variant of the NaCl-type of structure [Li4MoO5: 1379 Io(hkl), four-circle-diffractometer Philips PW 1100, ω-2Θ scan, AgKα-bar, R = 8.7% and Rw = 8.3%, space group P1-bar with a = 511.9(1), b = 772.7(2), c = 506.4(1) pm, α = 101.70(1)0, β = 101.48(1)0, γ = 108.58(2)0, Z = 2 and Li4WO5: 1027 I0(hkl), Philips PW 1100, ω-2Θ scan, MoKα-bar, R = 4.0% and Rw = 3.7%, space group P1-bar with a = 510.94(5), b = 771.59(7), c = 506.09(4) pm, α = 101.804(8)0, β = 101.78(1)0, γ = 108.770(9)0, Z = 2]. The structural relations are deduced from Schlegel Diagrams. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECON, these via Mean Fictive Ionic Radii, MEFIR, are calculated and discussed. (author)