Polymorphism of PrIr2Si2 – In situ XRPD experiments and theoretical calculations

We have confirmed polymorphism of PrIr2Si2 and performed the in situ high-temperature X-ray powder diffraction (XRPD) experiments focused on the dynamics of the crystallographic phase transition from the high-temperature CaBe2Ge2-type phase to the low-temperature ThCr2Si2 phase above 250 °C. A double-exponential time evolution of this phase transformation has been observed at 325 °C. We have also performed density functional calculations to analyze why the low-temperature crystallographic modification becomes the ground state crystal structure. The important role of the c/a ratio in this process can be argued from results of calculations.