THE STRUCTURE OF GAASO4-CENTER-DOT-2H(2)O - A NEW MEMBER OF THE VARISCITE FAMILY

GaAsO4 . 2H(2)O was synthesized hydrothermally from Ga2O3 and a K+-AsO 43--solution at pH=2. A single crystal structure determination showed that GaAsO4 . 2H(2)O is isotypic with variscite and therefore the firs t gallium arsenate with octahedrally coordinated Ga(III). Crystal data : space group Pbca, a = 1016, 0(1), b = 886,2(1), c = 994, 1(1) pm, R- g = 0,0266. GaAsO4 . 2H(2)O dehydrates at 439 K with formation of an a morphous material and poor crystalline GaAsO4. The crystal data of all known compounds with variscite structure have been compiled.