Pressure-induced softening in Cu2O

Recently, we have suggested that negative thermal expansion materials may also exhibit pressure-induced softening, where the elastic stiffness is anomalously reduced under compression. We propose to investigate whether Cu2O, a well-known NTE material, shows this effect, specifically focusing on whether B', the pressure derivative of bulk modulus, becomes negative. We expect that the value of B' in Cu2O will exhibit an interesting change from negative to positive due to its narrower NTE temperature range. Using neutron powder diffraction, we will perform measurements across different pressures and temperatures to characterize this effect. The experiment will be conducted using the normal setup Paris-Edinburgh V3 press with liquid nitrogen cooling at the PEARL diffractometer.