Neutron powder diffraction data of solid Propane collected in 2 K steps between 9.5 - 77.5 K

Neutron powder diffraction data collected from a condensed sample of propane (C3H8) with the Wombat high-intensity neutron diffraction instrument located at the OPAL reactor, Sydney, Australia. Data were collected at a wavelength of 2.422 Å. The files ending in .nx.hdf are raw data files conforming to the NeXus standard (see nexusformat.org). The files ending in .xye are three-column ASCII reduced data derived from the corresponding raw data NeXus file, with the columns being angle, intensity and standard uncertainty of that intensity. To obtain the reduced data from the raw data each pixel was multiplied by the corresponding value in the efficiency map contained in file 'eff_2025_02_27.gumtree.hdf’ after which all pixels at each angle were summed vertically and the final values output. As the sample contained a strong incoherent scatterer (hydrogen), additional steps were taken in data collection/reduction to alleviate the high background – known as gain re-refinement. For each temperature 8 frames of data were collected by stepping the detector by the pixel spacing, 0.125◦, which resulting in multiple measurements of the same signal at each angle after vertical summation. Scale factors for each column of vertical pixels are then refined using the procedure of Ford and Rollett (DOI 10.1107/s0567740868002190). This has been implemented on the Wombat instrument using the same underlying code described the Echidna instrument (DOI 10.1107/S1600576718014048), which should be referred to for details of the mathematics involved for this gain re-refinement. The detector/x_pixel_angular_offset raw data file entry gives the angular boundaries of each detector pixel. These values were used to derive pixel centres, which were then added to sample/azimuthal_angle to give the final angular values found in the reduced data file. Neutron powder diffraction data was collected in targeted 2 K steps, with the sample allowed to equilibrate after each temperature change. Please note the set temperatures recorded in the file names do not reflect the measured sample temperature – this can be extracted from each raw data file at the sample/tc2/sensor/sensorValueA data entry. (For instance reduced data file WBT0102742_C3H8_10_K.xye was collected at a measured temperature of 9.5 K)