The Crystal Structure of Silver Phosphate

A new value for the oxygen parameter in the structure of silver phosphate has been determined which gives the P–O separation in the phosphate group as 1.61A±0.03A. The value found here is slightly larger than that determined from an analysis of the crystal KH₂PO₄. The slight increase in P–O distance is explained on the basis of the nature of the phosphate group and of some covalent bond formation between oxygen and the surrounding silver atoms. To get qualitative agreement between calculated and observed intensities it was found necessary to treat the silver atoms as oscillators with tetragonal symmetry, the symmetry of their environments in the crystal. The ratio of the amplitudes of vibration along the tetragonal axis and perpendicular to it has been evaluated from the data. This result is discussed in relation to the structure of silver iodide.