Behaviour of polyhedra in Sr2NiMoO6 at high pressure and temperature

Abstract

The high-pressure behaviour of Sr 2 NiMoO 6 has been measured up to ∼6 GPa using neutron powder diffraction. With increasing pressure the tetragonal ( 4∕ ) symmetry is maintained and the structure becomes more distorted. The distortion is a result of increased octahedral tilting away from the idealised cubic symmetry by rotation around the -axis in the plane. The pressure equation of state has been determined and gives values of 0 =243.10(2) Å 3 , 0 =155(2) GPa and ′ =3.1(6). We also report the high temperature behaviour at ambient pressure and observe a transition from tetragonal to cubic symmetry at ∼ 573 K.