Tilting and distortion of CaSnO_3 perovskite to 7 GPa determined from single-crystal X-ray diffraction

摘要

The structural changes of CaSnO3, a GdFeO3-type perovskite, have been investigated to 7 GPa in a diamond-anvil cell at room temperature using single-crystal X-ray diffraction. Significant changes are observed in both the octahedral Sn–O bond lengths and tilt angles between the SnO6 octahedra. The octahedral (SnO_6) site shows anisotropic compression and consequently the distortion of SnO6 increases with pressure. Increased pressure also results in a decrease of both of the inter-octahedral angles, ∠Sn–O_1–Sn and ∠Sn–O_2–Sn, indicating that octahedral tilting increases with increasing pressure, chiefly equivalent to rotation of the SnO_6 octahedra about the pseudocubic <001>p axis. The distortion in the CaO_(12) and SnO_6 sites, along with the octahedral SnO_6 tilting, is attributed to the SnO6 site being less compressible than the CaO_(12) site.