The compound, Si5O(PO4)6, is a component of a solid phosphoric acid catalyst, it has highly unusual coordination of the silicon (octahedral, as well as the more common tetrahedral). . Silicon oxide phosphate¿s three dimensional structure shows a network with cavities when viewed down the a-axis, likely enabling transport of oxide ions or protons through these channels. We aim to study the structure of Si5O(PO4)6 probing the evolution of structure, especially coordination polyhedral as temperature is increased. In particular we anticipate there may be changes in the coordination between sixfold and fourfold units along the c axis as temperature is increased. Secondly we wish to probe the mechanism of reaction to produce this channel structure on heating. Finally we wish to probe the deuterium location in some hydrothermally treated samples and to investigate similar compositions