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Sm6Fe6As6O5F crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. there are four inequivalent Sm+2.83+ sites. In the first Sm+2.83+ site, Sm+2.83+ is bonded in a 4-coordinate geometry to four As3- and four O2- atoms. There are a spread of Sm–As bond distances ranging from 3.30–3.32 Å. There are a spread of Sm–O bond distances ranging from 2.33–2.36 Å. In the second Sm+2.83+ site, Sm+2.83+ is bonded in a 4-coordinate geometry to four As3-, three O2-, and one F1- atom. There are two shorter (3.23 Å) and two longer (3.32 Å) Sm–As bond lengths. There are one shorter (2.26 Å) and two longer (2.33 Å) Sm–O bond lengths. The Sm–F bond length is 2.42 Å. In the third Sm+2.83+ site, Sm+2.83+ is bonded in a 4-coordinate geometry to four As3-, three O2-, and one F1- atom. There are a spread of Sm–As bond distances ranging from 3.22–3.34 Å. There are a spread of Sm–O bond distances ranging from 2.28–2.34 Å. The Sm–F bond length is 2.44 Å. In the fourth Sm+2.83+ site, Sm+2.83+ is bonded in a 4-coordinate geometry to four As3-, three O2-, and one F1- atom. There are two shorter (3.22 Å) and two longer (3.31 Å) Sm–As bond lengths. There are one shorter (2.27 Å) and two longer (2.31 Å) Sm–O bond lengths. The Sm–F bond length is 2.45 Å. There are four inequivalent Fe2+ sites. In the first Fe2+ site, Fe2+ is bonded to four As3- atoms to form a mixture of edge and corner-sharing FeAs4 tetrahedra. There are a spread of Fe–As bond distances ranging from 2.61–2.63 Å. In the second Fe2+ site, Fe2+ is bonded to four As3- atoms to form a mixture of edge and corner-sharing FeAs4 tetrahedra. There are one shorter (2.59 Å) and three longer (2.61 Å) Fe–As bond lengths. In the third Fe2+ site, Fe2+ is bonded to four As3- atoms to form a mixture of edge and corner-sharing FeAs4 tetrahedra. There are a spread of Fe–As bond distances ranging from 2.61–2.63 Å. In the fourth Fe2+ site, Fe2+ is bonded to four As3- atoms to form a mixture of edge and corner-sharing FeAs4 tetrahedra. All Fe–As bond lengths are 2.62 Å. There are four inequivalent As3- sites. In the first As3- site, As3- is bonded in a 8-coordinate geometry to four Sm+2.83+ and four Fe2+ atoms. In the second As3- site, As3- is bonded in a 8-coordinate geometry to four Sm+2.83+ and four Fe2+ atoms. In the third As3- site, As3- is bonded in a 8-coordinate geometry to four Sm+2.83+ and four Fe2+ atoms. In the fourth As3- site, As3- is bonded in a 8-coordinate geometry to four Sm+2.83+ and four Fe2+ atoms. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to four Sm+2.83+ atoms to form OSm4 tetrahedra that share corners with two equivalent OSm4 tetrahedra, corners with two equivalent FSm4 tetrahedra, and edges with four OSm4 tetrahedra. In the second O2- site, O2- is bonded to four Sm+2.83+ atoms to form distorted OSm4 tetrahedra that share corners with four OSm4 tetrahedra, an edgeedge with one FSm4 tetrahedra, and edges with three OSm4 tetrahedra. In the third O2- site, O2- is bonded to four Sm+2.83+ atoms to form distorted OSm4 tetrahedra that share a cornercorner with one FSm4 tetrahedra, corners with three OSm4 tetrahedra, an edgeedge with one FSm4 tetrahedra, and edges with three OSm4 tetrahedra. F1- is bonded to four Sm+2.83+ atoms to form distorted FSm4 tetrahedra that share corners with four OSm4 tetrahedra and edges with four OSm4 tetrahedra.

36 MATERIALS SCIENCE↗