Die Kristallstruktur von TIZnPO4 und TIZnAsO4 / The Crystal Structure of TIZnPO4 and TIZnAsO4

Abstract

Single crystals of the title com pounds were obtained by high pressure synthesis in a modified Belt type apparatus. The compounds crystallize in the monoclinic system (space group P21) with a = 8.732(2), b = 5.468(1), c = 8.841(2) Å, β = 90.61(2)° for TlZnPO4 and a = 8.921(3), b = 5.631(1), c = 8.958(3) Å, β = 91.03(2)° for TlZnAsO4, Z = 4. The structures were refined from diffractom eter data to R = 0.072, Rw = 0.050 for 3700 (TlZnPO4) and to R = 0.093, Rw = 0.067 for 3943 (TlZnAsO4) independent absorption corrected reflections. The compounds are isotypic and belong to the “stuffed derivatives" of the Icmm structure type with a (ZnXO4)- network of alternating corner linked ZnO4 and XO4 tetrahedra (X = P, As) forming channels of six-membered rings in the direction of the a axis. These cavities contain two crystallographically independent Tl cations in an irregular coordination by eight nearest oxygen atoms