Even though the effects of radiation damage are reduced at low temperatures (Goeta & Howard, 2004 ), the GPI crystal exhibits a steady increase in volume that is correlated to the duration of synchrotron X-ray irradiation. Thus, two effects are acting on the GPI crystal in the synchrotron study: the first is the influence of cooling, and the second, more dominant, impact is that of the radiation damage. In the laboratory experiment, a volume contraction of 1.2% is observed upon cooling to 100 K, in contrast to the volume expansion of 0.4% recorded in the synchrotron study. Most striking is the completely different thermal expansion response of GPI upon cooling. Since this suggests the possibility of radiation damage, the authors complemented their synchrotron study with a similar experiment using a laboratory diffractometer. However, a deterioration of the data quality is observed upon cooling, manifested by a suppression of scattering at high angles and an increase of atomic displacement parameters for all atoms. Since the ferroelectric behaviour is associated with an ordering of light hydrogen atoms and rearrangement of hydrogen bonds, single-crystal diffraction is favoured over the faster powder diffraction measurements. At the European Synchrotron Radiation Facility (ESRF), they performed variable-temperature single-crystal diffraction measurements in fine-temperature steps to fully characterize the order parameters and strains involved in the ferroelectric transition of GPI. (2021 ) published in this issue, the authors tackle these questions with their study on the molecular ferroelectric crystal glycinium phosphite (GPI), which has the chemical formula NH 3CH 2COOH temperature or pressure, but also with the duration of X-ray irradiation, how can these two effects be separated? Furthermore, if the sample does exhibit radiation damage, will this reduce or enhance material functionality in other words, could we begin to use radiation to fine-tune properties on the micron to nanoscale? If the sample is changing not only as a function of applied stimulus, e.g. This is especially important for in situ studies, where the material of interest is investigated as a function of various external conditions and measured multiple times. With the increasing use of third- and fourth-generation synchrotrons, the small-molecule crystallographic community has recently begun to assess the radiation damage impact of high intensity beams on samples.
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