Difference in bond length

Consider the material GaPO₄

Figure 3.3: PDFs of iso-structural Quartz and GaPO₄ - provided by Helen Playford 

The two materials are isotypic, i.e. they have structures of a similar type. The main difference is that in GaPO₄ there are alternating Ga and P atoms through the structure. However, as can be seen from the PDFs, there is a notable difference in the Ga-O and P-O bond lengths in the polyhedra that form this structure. This can have a strong influence on the physical properties e.g. the Piezo-electric properties. The PDF can therefore provide vital information on these local environments and be used to tune and understand the properties of these functional oxides.