| Abstrakt: |
Ab initiocrystal structure determination of the αform of MnHP2O7and Rietveld refinement of the MnLiP2O7structure were performed using powder X-ray diffraction data. The final structures have been obtained using soft restraints on interatomic bond lengths and bond angles for the diphosphate group. The two compounds were found to be to a great extent isostructural. They crystallize in the monoclinic space group P21, Z= 2, a= 6.7547(6), b= 8.3160(7), c= 4.8769(5) Å, β= 113.1791(18)°, Rp= 0.0283, Rwp= 0.0390, RBragg= 0.0930, RF= 0.0869 for α-MnHP 22O7, and a= 7.0018(5), b= 8.1616(6), c= 4.7267(4)Å, β= 109.404(3)°, Rp= 0.0307, Rwp= 0.0423, RBragg= 0.0960, RF= 0.0861 for MnLiP2O7. In both compounds, diphosphate groups adopt nearly eclipsed configuration. Their structures present three-dimensional networks, which have tunnels including the lithium cations or hydrogen atoms. The behaviour of the crystalline forms of MnHP2O7in H/Li exchange reactions is discussed, vs. their structural aspects. |
