Materials Data on La2HfO5 by Materials Project

Abstract

La2HfO5 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent La3+ sites. In the first La3+ site, La3+ is bonded to seven O2- atoms to form distorted LaO7 hexagonal pyramids that share corners with three equivalent HfO5 trigonal bipyramids, edges with two equivalent LaO7 hexagonal pyramids, and edges with two equivalent HfO5 trigonal bipyramids. There are a spread of La–O bond distances ranging from 2.42–2.59 Å. In the second La3+ site, La3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of La–O bond distances ranging from 2.48–2.58 Å. Hf4+ is bonded to five O2- atoms to form distorted HfO5 trigonal bipyramids that share corners with three equivalent LaO7 hexagonal pyramids, corners with two equivalent HfO5 trigonal bipyramids, and edges with two equivalent LaO7 hexagonal pyramids. There are a spread of Hf–O bond distances ranging from 1.94–2.08 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded to four La3+ atoms to form a mixture of edge and corner-sharing OLa4 tetrahedra. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent La3+ and one Hf4+ atom. In the third O2- site, O2- is bonded to three La3+ and one Hf4+ atom to form OLa3Hf tetrahedra that share corners with eight OLa4 tetrahedra and edges with two equivalent OLa3Hf tetrahedra. In the fourth O2- site, O2- is bonded to three La3+ and one Hf4+ atom to form a mixture of distorted edge and corner-sharing OLa3Hf tetrahedra. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to two La3+ and two equivalent Hf4+ atoms.