DOE OSTI2020
Ca2MgFe(CO3)4 is Calcite-derived structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with two equivalent MgO6 octahedra and corners with four equivalent FeO6 octahedra. The corner-sharing octahedra tilt angles range from 57–67°. There are a spread of Ca–O bond distances ranging from 2.36–2.45 Å. In the second Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with two equivalent FeO6 octahedra and corners with four equivalent MgO6 octahedra. The corner-sharing octahedra tilt angles range from 56–66°. There are a spread of Ca–O bond distances ranging from 2.38–2.41 Å. Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six CaO6 octahedra. The corner-sharing octahedra tilt angles range from 56–66°. There are a spread of Mg–O bond distances ranging from 2.11–2.15 Å. Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six CaO6 octahedra. The corner-sharing octahedra tilt angles range from 57–67°. There are a spread of Fe–O bond distances ranging from 2.12–2.25 Å. There are four inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a trigonal planar geometry to three O2- atoms. All C–O bond lengths are 1.30 Å. In the second C4+ site, C4+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of C–O bond distances ranging from 1.29–1.31 Å. In the third C4+ site, C4+ is bonded in a trigonal planar geometry to three O2- atoms. All C–O bond lengths are 1.30 Å. In the fourth C4+ site, C4+ is bonded in a trigonal planar geometry to three O2- atoms. There is two shorter (1.29 Å) and one longer (1.30 Å) C–O bond length. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+, one Mg2+, and one C4+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+, one Fe2+, and one C4+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+, one Mg2+, and one C4+ atom. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Fe2+, and one C4+ atom. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+, one Mg2+, and one C4+ atom. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+, one Fe2+, and one C4+ atom. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+, one Mg2+, and one C4+ atom. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+, one Fe2+, and one C4+ atom. In the ninth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+, one Fe2+, and one C4+ atom. In the tenth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+, one Mg2+, and one C4+ atom. In the eleventh O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+, one Mg2+, and one C4+ atom. In the twelfth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+, one Fe2+, and one C4+ atom.