We combine the extended finite element method with simulations of diffracted x-ray intensities to investigate the diffusely scattered intensity due to dislocations. As a model system a thin PbSe epitaxial layer grown on top of a PbTe buffer on a CdTe substrate was chosen. The PbSe film shows a periodic dislocation network where the dislocations run along the orthogonal ⟨110⟩ directions. The array of dislocations within this layer can be described by a short range order model with a narrow distribution.