X-ray diffuse scattering from disordered alloys is the primary direct source of information concerning the Warren parameters which describe the existing state of order. However, the short range order diffuse intensity is obscured by other contributions to the diffraction pattern resulting from static atomic displacements from the average lattice, and from effects related to thermal motion. Described here is a method to separate the diffraction pattern into its various components so that each may be interpreted independently. No assumptions are made about the nature of the atomic displacements δ, except that they are sufficiently small, and that the diffraction vector k/2π is sufficiently small, that terms beyond the term quadratic in k ^. δ may be neglected in the series expansion of exp [ik ^. δ].

To construct a three-dimensional model of the local atomic arrangements for solid solutions, it is preferable to have X-ray diffuse scattering measurements in three-dimensional space. Two such measurements have been made on a single-crystal of Ni₄Mo as quenched from 1000°C and as annealed for 5 min at 650°C.