Investigation of the mosaic structure of RbI single crystals in the metastable pressure region with 412 keV γrays

Abstract
Pressure-induced changes of the mosaic structures in RbI crystals, with a thermodynamic equilibrium between the low-pressure NaCl phase and the high-pressure CsCl phase at 3.56 kbar, have been investigated by means of 412 keV gamma rays up to pressures of 4.2 kbar. The effects observed were much more pronounced in crystals previously heated for 24 hours very near the melting point (642 degrees C). The mosaic structure remained relatively unaffected by pressure cycles with a maximum pressure below 3.5 kbar. However, when the maximum pressure in the pressure cycle was increased above 3.5 kbar, drastic changes were observed in the integrated intensity and width of the rocking curve. It seems that the pressure cycles applied tend to stabilise the low-pressure NaCl phase in the metastable pressure region.