Synchrotron single crystal X-ray diffraction measurements showed the presence of weak structured diffuse scattering, consisting of rods lying along 100 * type directions [ESI Fig. ]. The intensity of the diffuse scattering decayed with increasing scattering vector, Q, implying that the diffuse scattering is produced primarily by correlated substitutional disorder, most likely vacancy ordering, rather than displacive disorder. The asymmetric distribution of intensity around each Bragg peak additionally suggests that the structure relaxes around these vacancies. Future analysis will focus on gaining quantitative understanding of vacancy order.