Main group metal iodometallate represent a large class of semiconducting materials which display optical and electronic properties of current great interest in relation to the sensitisation of solar cells for water splitting. Of particular interest are the heavy group 14 iodometalates, since they can adopt perovskitic structures of varying dimensionality and demonstrate large compositional and structural variations. The orientation of the alkyl groups or water molecules in the structures and role of hydrogen bonding are key aspects that define the type of structure formed and therefore the derived electronic and optical properties. In this experiment we will study several key materials of this type in order to define the positions and orientations of the hydrogen containing sections of the structure ¿ particularly the [- NH3]+ groups - such information only be obtained from NPD data.