Redetermination of the crystal structure of image, and its thermal behaviour in the range image

The crystal structure of image image was redetermined using X-ray powder diffraction methods. Reindexing the pattern showed that the monoclinic angle is image and the lattice parameters image, image, image, rather than the reported image, image, image, image in space group image. 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 image in the temperature range from 300 to 16 K. image 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.