DOE OSTI2020
NaErO2 is Caswellsilverite-like structured and crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to six O2- atoms to form NaO6 octahedra that share corners with two equivalent NaO6 octahedra, corners with four ErO6 octahedra, edges with five NaO6 octahedra, and edges with seven ErO6 octahedra. The corner-sharing octahedra tilt angles range from 0–14°. There are a spread of Na–O bond distances ranging from 2.39–2.71 Å. In the second Na1+ site, Na1+ is bonded to six O2- atoms to form NaO6 octahedra that share corners with two equivalent NaO6 octahedra, corners with four ErO6 octahedra, edges with five NaO6 octahedra, and edges with seven ErO6 octahedra. The corner-sharing octahedra tilt angles range from 7–14°. There are four shorter (2.42 Å) and two longer (2.73 Å) Na–O bond lengths. There are two inequivalent Er3+ sites. In the first Er3+ site, Er3+ is bonded to six O2- atoms to form ErO6 octahedra that share corners with two equivalent ErO6 octahedra, corners with four NaO6 octahedra, edges with five ErO6 octahedra, and edges with seven NaO6 octahedra. The corner-sharing octahedra tilt angles range from 7–14°. There are a spread of Er–O bond distances ranging from 2.27–2.30 Å. In the second Er3+ site, Er3+ is bonded to six O2- atoms to form ErO6 octahedra that share corners with two equivalent ErO6 octahedra, corners with four NaO6 octahedra, edges with five ErO6 octahedra, and edges with seven NaO6 octahedra. The corner-sharing octahedra tilt angles range from 0–14°. There are four shorter (2.28 Å) and two longer (2.29 Å) Er–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to three Na1+ and three Er3+ atoms to form a mixture of distorted edge and corner-sharing ONa3Er3 octahedra. The corner-sharing octahedra tilt angles range from 2–12°. In the second O2- site, O2- is bonded to three Na1+ and three Er3+ atoms to form a mixture of edge and corner-sharing ONa3Er3 octahedra. The corner-sharing octahedra tilt angles range from 3–12°.