HIGHLY ORDERED DISTRIBUTION OF THE INTERPOLATED UNIVALENT CATIONS IN MONOPHOSPHATES WITH THE ALPHA-K2MO2O3(PO4)(2) STRUCTURE

The structure of four Mo(V) monophosphates - K0.43Cs1.5Mo2O3(PO4)(2), KCsMo2O3(PO4)(2), K1.26Cs0.74Mo2O3(PO4)(2) and K0.88Rb1.12Mo2O3(PO4)(2 ) - has been determined from single crystal X ray diffraction study. A ll these compounds crystallize in the P2(1)/c space group and exhibit the alpha-K2Mo2O3(PO4)(2) structure built up from bioctahedral Mo2O11 units and monophosphate groups forming intersecting tunnels. The origi nal character of these phosphates deals with the highly ordered distri bution of the interpolated cations over the three sites A(1), A(2) and A(3) of the tunnels;the latter are indeed first occupied by potassium with the following occupancy A(1) A(3) - A(2), all of them being avai lable also for rubidium and thallium, whereas the A(1) site is too sma ll to be occupied by cesium.