In situ structural study of metastable states during boron crystallization at high-pressure

Boron allotropy is a fertile source of structural diversity and a very active field, as exemplified by the latest boron occurrences: borophene and all-boron fullerenes. Reaction conditions, post-synthetic treatments and the nature of the starting material are some of the most important parameters guiding the selective formation of a given phase. We recently investigated by in situ XRD the crystallization of nanostructured amorphous boron. We observed the appearance of an unidentified boron compound at high pressure (5 GPa), which is unstable upon decompression. However, the former experiment was performed by using polychromatic light at PSICHE beamline at SOLEIL. With the present experiment, we aim at an in-depth characterization of the named compound from a structural point of view, by analysing the crystallization pathways. In situ high quality-angular dispersive X-ray diffraction will be instrumental to determine and refine the structure of a possible new boron allotrope.