Redetermination of the crystal structure of Ge(HPO4)2·H2OGe(HPO4)2·H2O, and its thermal behaviour in the range 300⩾T⩾16K

The crystal structure of α-Ge(HPO4)2·H2Oα-Ge(HPO4)2·H2O(α-GeP)(α-GeP) was redetermined using X-ray powder diffraction methods. Reindexing the pattern showed that the monoclinic angle is β=108.985(1)∘β=108.985(1)∘ and the lattice parameters a=8.2920(2)Å, b=4.7880(1)Å, c=16.4058(3)Å, rather than the reported β=110.2(4)∘β=110.2(4)∘, a=8.230(2)Å, b=4.784(1)Å, c=16.502(5)Å in space group P21/cP21/c. This apparently minor change in the cell parameters is important as it otherwise leads to incorrect Ge–O and P–O distances. Variable temperature X-ray diffraction experiments give an insight into the thermal behaviour of α-GePα-GeP in the temperature range from 300 to 16 K. α-GePα-GeP behaves as expected for a layered structure, showing a much larger expansion perpendicular to the layers than within the layers. The monoclinic angle increases with decreasing temperature. No temperature induced phase transitions have been observed in the temperature interval studied.

The crystal structure of αα-GeP has been redetermined. It is confirmed that αα-GeP has αα-ZrP type structure. An interpretation for the geometrical trends in αα-ZrP type APTM   is suggested. The thermal behaviour of αα-GeP has been from 300 to 16 K. No structural phase transitions have been observed.Figure optionsDownload full-size imageDownload as PowerPoint slide