CHIMIE DOUCE SYNTHESIS AND AB-INITIO STRUCTURE DETERMINATION OF (H3O)YB3F10, H2O - A DIAMOND-TYPE STACKING OF UOA([8])

The fluoride (H3O)Yb3F10, H2O (SG:<Fd(3)over bar m>, a = 15.326(1)Angs trom, Z = 16) was synthesized in the form of powder by a ''chimie douc e'' route. The compound delta-KYb3F10,H2O (SG:<Fd(3)over bar m>, a = 1 5.339(1) Angstrom, Z = 16), a new member of the KYb3F10 family, was ob tained by an acid-base neutralization. The structural description is b ased upon the stacking of [Yb6F32](14-) ''octahedral units of antipris m,'' called UOA([8]), where the three-dimensional [Yb6F20](2-) network is simply a diamond type stacking of UOA([8]) connected by vertices. The counterions are located in the middle of the chair hexagons. The z eolithic character of the water molecules is related to their mobility through the tunnels of this diamond structure. The simplifying descri ption of this phase as a diamond type structure built up from UOA([8]) (A(2)[Yb6F20], 2H(2)O, A = H3O+, Z = 8) is the basis of our reexamina tion of the structural description of numerous complex structures buil t up of antiprisms. (C) 1997 Academic Press.