Monoclinic distortion in the insulating phase of PrNiO3

Single crystals of PrNiO3 perovskite were grown under 4.5 GPa with NaCl and KCl flux. The electron diffraction and single crystal synchrotron X-ray diffraction experiments clearly detected the presence of a monoclinic distortion (space group P21/n) below the metal-insulator transition temperature TMI, which implies the splitting of the Ni sites in the crystal in the insulating state