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La0.7Ca0.3MnO3 (a = 3.86 angstroms) epitaxial thin films have been grown on SrTiO3 (a = 3.905 angstroms), LaAlO3 (a = 3.79 angstroms), and YAlO3 (a/square root of 2 = 3.66 angstroms, b/square root of 2 = 3.77 angstroms) substrates. The films were analyzed with x-ray diffraction, x-ray photoemission spectroscopy, dc and ac resistivity, and dc magnetization.
CaMnO3 is (Cubic) Perovskite-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to twelve O2- atoms to form CaO12 cuboctahedra that share corners with six equivalent CaO12 cuboctahedra, corners with six equivalent MnO6 octahedra, faces with eight CaO12 cuboctahedra, and faces with six equivalent MnO6 octahedra. The corner-sharing octahedral tilt angles are 14°. There are six shorter (2.70 Å) and six longer (2.83 Å) Ca–O bond lengths. In the second Ca2+ site, Ca2+ is bonded to twelve O2- atoms to form CaO12 cuboctahedra that share corners with twelve equivalent CaO12 cuboctahedra, faces with six equivalent CaO12 cuboctahedra, and faces with eight equivalent MnO6 octahedra. There are six shorter (2.70 Å) and six longer (2.78 Å) Ca–O bond lengths. Mn4+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with three equivalent CaO12 cuboctahedra, corners with three equivalent MnO6 octahedra, faces with seven CaO12 cuboctahedra, and a faceface with one MnO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There is three shorter (1.88 Å) and three longer (1.93 Å) Mn–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted linear geometry to four Ca2+ and two equivalent Mn4+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to four Ca2+ and two equivalent Mn4+ atoms.
Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations
CaMn4O8 crystallizes in the orthorhombic Cmc2_1 space group. The structure is three-dimensional. Ca2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ca–O bond distances ranging from 2.19–2.84 Å. There are three inequivalent Mn+3.50+ sites. In the first Mn+3.50+ site, Mn+3.50+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing MnO6 octahedra. The corner-sharing octahedral tilt angles are 48°. There are a spread of Mn–O bond distances ranging from 1.91–1.96 Å. In the second Mn+3.50+ site, Mn+3.50+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing MnO6 octahedra. The corner-sharing octahedra tilt angles range from 53–56°. There are a spread of Mn–O bond distances ranging from 1.94–2.07 Å. In the third Mn+3.50+ site, Mn+3.50+ is bonded to six O2- atoms to form a mixture of distorted edge and corner-sharing MnO6 octahedra. The corner-sharing octahedra tilt angles range from 48–56°. There are a spread of Mn–O bond distances ranging from 1.94–2.55 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded to one Ca2+ and three Mn+3.50+ atoms to form distorted corner-sharing OCaMn3 trigonal pyramids. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+ and three Mn+3.50+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+ and three Mn+3.50+ atoms. In the fourth O2- site, O2- is bonded to one Ca2+ and three Mn+3.50+ atoms to form distorted corner-sharing OCaMn3 tetrahedra. In the fifth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Mn+3.50+ atoms. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+ and three Mn+3.50+ atoms.
Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations