DOE OSTI2020
Nd2Zr2O7 crystallizes in the orthorhombic Pmma space group. The structure is three-dimensional. there are two inequivalent Nd3+ sites. In the first Nd3+ site, Nd3+ is bonded to six O2- atoms to form a mixture of distorted corner and edge-sharing NdO6 octahedra. The corner-sharing octahedral tilt angles are 73°. There are four shorter (2.37 Å) and two longer (2.39 Å) Nd–O bond lengths. In the second Nd3+ site, Nd3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are four shorter (2.27 Å) and two longer (2.42 Å) Nd–O bond lengths. There are two inequivalent Zr4+ sites. In the first Zr4+ site, Zr4+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.17–2.62 Å. In the second Zr4+ site, Zr4+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.22–2.41 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded to three Nd3+ and one Zr4+ atom to form a mixture of distorted corner and edge-sharing ONd3Zr tetrahedra. In the second O2- site, O2- is bonded to four Zr4+ atoms to form distorted OZr4 tetrahedra that share corners with sixteen ONd3Zr tetrahedra and edges with six ONdZr3 tetrahedra. In the third O2- site, O2- is bonded to one Nd3+ and three Zr4+ atoms to form a mixture of corner and edge-sharing ONdZr3 tetrahedra. In the fourth O2- site, O2- is bonded to two equivalent Nd3+ and two equivalent Zr4+ atoms to form ONd2Zr2 tetrahedra that share corners with fourteen ONd3Zr tetrahedra and edges with five OZr4 tetrahedra. In the fifth O2- site, O2- is bonded to two equivalent Nd3+ and two equivalent Zr4+ atoms to form a mixture of corner and edge-sharing ONd2Zr2 tetrahedra.