DOE OSTI2020
Ce2O2FeSe2 crystallizes in the orthorhombic Cmc2_1 space group. The structure is three-dimensional. there are four inequivalent Ce3+ sites. In the first Ce3+ site, Ce3+ is bonded in a 4-coordinate geometry to four Se2- and four O2- atoms. There are two shorter (3.20 Å) and two longer (3.43 Å) Ce–Se bond lengths. There are a spread of Ce–O bond distances ranging from 2.32–2.41 Å. In the second Ce3+ site, Ce3+ is bonded in a 4-coordinate geometry to four Se2- and four O2- atoms. There are two shorter (3.19 Å) and two longer (3.38 Å) Ce–Se bond lengths. There are a spread of Ce–O bond distances ranging from 2.36–2.45 Å. In the third Ce3+ site, Ce3+ is bonded in a 3-coordinate geometry to five Se2- and three O2- atoms. There are a spread of Ce–Se bond distances ranging from 3.15–3.25 Å. There are one shorter (2.33 Å) and two longer (2.37 Å) Ce–O bond lengths. In the fourth Ce3+ site, Ce3+ is bonded in a 3-coordinate geometry to five Se2- and three O2- atoms. There are a spread of Ce–Se bond distances ranging from 3.07–3.33 Å. There are one shorter (2.34 Å) and two longer (2.36 Å) Ce–O bond lengths. There are two inequivalent Fe2+ sites. In the first Fe2+ site, Fe2+ is bonded in a distorted linear geometry to four Se2- and two O2- atoms. There are two shorter (2.87 Å) and two longer (2.88 Å) Fe–Se bond lengths. Both Fe–O bond lengths are 1.99 Å. In the second Fe2+ site, Fe2+ is bonded to four Se2- atoms to form distorted corner-sharing FeSe4 tetrahedra. There are a spread of Fe–Se bond distances ranging from 2.55–2.63 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 1-coordinate geometry to six Ce3+ and one Fe2+ atom. In the second Se2- site, Se2- is bonded in a 6-coordinate geometry to six Ce3+ atoms. In the third Se2- site, Se2- is bonded in a 6-coordinate geometry to two Ce3+ and four Fe2+ atoms. In the fourth Se2- site, Se2- is bonded in a 1-coordinate geometry to four Ce3+ and three Fe2+ atoms. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to four Ce3+ atoms to form a mixture of edge and corner-sharing OCe4 tetrahedra. In the second O2- site, O2- is bonded to four Ce3+ atoms to form a mixture of edge and corner-sharing OCe4 tetrahedra. In the third O2- site, O2- is bonded to three Ce3+ and one Fe2+ atom to form a mixture of edge and corner-sharing OCe3Fe tetrahedra. In the fourth O2- site, O2- is bonded to three Ce3+ and one Fe2+ atom to form a mixture of edge and corner-sharing OCe3Fe tetrahedra.