*2.5. Powder X-ray Di*ff*raction Investigations*

Powder X-ray diffraction (PXRD) data were collected on a Bruker D8 Advance X-ray diffractometer (Bruker AXS GmbH, Karlsruhe, Germany) equipped with a Vario attachment and Vantec linear PSD, using Cu radiation (40 kV, 40 mA) monochromated by a curved Johansson monochromator (λ Cu Kα<sup>1</sup> 1.5406 Å). Room-temperature data were collected in the reflection mode with a flat-plate sample. Samples were applied on the surface of a standard zero diffraction silicon plate. The samples were kept spinning (15 rpm) throughout the data collection. Patterns were recorded in the 2θ range between 3◦ and 90◦, in 0.008◦ steps, with a step time of 0.1–4.0 s. Several diffraction patterns in various experimental modes were collected for the samples. Processing of the data obtained was performed using EVA [39], indexing of powder data and crystal structure solving of β-*rac***-1** were carried out with TOPAS [40], and EXPO2014 [41] software packages.
