High-pressure NTE in niobium oxyfluoride at low temperature

NbO2F and TaO2F have extremely similar long- and short-range atomic structures, but exhibit significantly different thermal expansion behaviours (one positive, the other negative). At high pressure, both materials exhibit a cubic to rhombohedral transition, the origin of which is closely linked to anomalous thermal expansion behaviour. This experiment seeks to investigate the influence of high pressure on thermal expansion in NbO2F, to see whether it can be switched from positive to negative behaviour.