DOE OSTI2020
Pr4I5Ni crystallizes in the orthorhombic Pmmn space group. The structure is three-dimensional. there are three inequivalent Pr sites. In the first Pr site, Pr is bonded to one Ni and five I atoms to form a mixture of distorted edge and corner-sharing PrNiI5 octahedra. The corner-sharing octahedra tilt angles range from 2–11°. The Pr–Ni bond length is 2.81 Å. There are a spread of Pr–I bond distances ranging from 3.23–3.43 Å. In the second Pr site, Pr is bonded to two equivalent Ni and four I atoms to form a mixture of edge and corner-sharing PrNi2I4 octahedra. The corner-sharing octahedra tilt angles range from 0–11°. Both Pr–Ni bond lengths are 2.84 Å. There are two shorter (3.37 Å) and two longer (3.39 Å) Pr–I bond lengths. In the third Pr site, Pr is bonded to two equivalent Ni and four I atoms to form PrNi2I4 octahedra that share corners with four equivalent PrNi2I4 octahedra and edges with eight PrNiI5 octahedra. The corner-sharing octahedra tilt angles range from 0–1°. Both Pr–Ni bond lengths are 2.87 Å. There are two shorter (3.30 Å) and two longer (3.40 Å) Pr–I bond lengths. Ni is bonded to six Pr atoms to form edge-sharing NiPr6 octahedra. There are three inequivalent I sites. In the first I site, I is bonded in a 3-coordinate geometry to three Pr atoms. In the second I site, I is bonded in a distorted see-saw-like geometry to four Pr atoms. In the third I site, I is bonded in a square co-planar geometry to four Pr atoms.