Onyx detector

X-ray data were collected using an Agilent Xcalibur X-ray diffractometer with a Nova X-ray source and an Onyx detector (Agilent Technologies, Santa Clara, California, USA) using the following parameters: 50 kV, 0.8 mA, crystal-to-detector distance of 65.000 mm, θ (the detector angle) of 3.5°, oscillation width of 0.25°, number of frames = 2 × 6 separated by 90° and exposure time 15 s. Data were processed with CrysAlis^Pro in Pre-experiment mode, which outputs unit-cell parameters, an estimate of the diffraction limit and mosaicity. In CrysAlis^Pro, the ‘mosaicity’ is given as three components, e₁, e₂ and e₃, which are the mosaicities in three directions defined in a coordinate system local to each reflection. e₁ and e₂ are the mosaicities (i.e. the angle subtended by the diffraction spots) in two orthogonal directions tangential to the Ewald sphere (on the image, e₂ is the mosaicity along the direction radial from the beam center), while e₃ is the mosaicity in a direction perpendicular to e₁ and S − S₀, which is roughly the mosaicity in the scanning direction. Here, S and S₀ are the scattered and incident X-ray vectors, respectively (Kabsch, 2001 ▶ ). To allow the detection of asymmetric cooling effects, we started with unit-cell parameters unconstrained by space-group symmetry.