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MgO2 is Calaverite structured and crystallizes in the monoclinic C2/m space group. The structure is two-dimensional and consists of one MgO2 sheet oriented in the (0, 0, 1) direction. Mg is bonded to six equivalent O atoms to form distorted edge-sharing MgO6 octahedra. There are two shorter (2.01 Å) and four longer (2.12 Å) Mg–O bond lengths. O is bonded in a trigonal non-coplanar geometry to three equivalent Mg atoms.
MgO2 is Calaverite structured and crystallizes in the monoclinic C2/m space group. The structure is two-dimensional and consists of one MgO2 sheet oriented in the (0, 0, 1) direction. Mg is bonded to six equivalent O atoms to form distorted edge-sharing MgO6 octahedra. There are four shorter (2.07 Å) and two longer (2.16 Å) Mg–O bond lengths. O is bonded in a trigonal non-coplanar geometry to three equivalent Mg atoms.
MgO2 is Pyrite-like structured and crystallizes in the cubic Pa-3 space group. The structure is three-dimensional. Mg is bonded to six equivalent O atoms to form MgO6 octahedra that share corners with twelve equivalent MgO6 octahedra and corners with six equivalent OMg3O tetrahedra. The corner-sharing octahedral tilt angles are 69°. All Mg–O bond lengths are 2.11 Å. O is bonded to three equivalent Mg and one O atom to form OMg3O tetrahedra that share corners with three equivalent MgO6 octahedra and corners with fifteen equivalent OMg3O tetrahedra. The corner-sharing octahedral tilt angles are 72°. The O–O bond length is 1.51 Å.
MgO2 is pyrite-like structured and crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Mg is bonded to six equivalent O atoms to form edge-sharing MgO6 octahedra. All Mg–O bond lengths are 2.11 Å. O is bonded in a 4-coordinate geometry to three equivalent Mg and one O atom. The O–O bond length is 1.49 Å.
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
(MgO2)3Mg3Si4O12 crystallizes in the triclinic P1 space group. The structure is two-dimensional and consists of two Mg3Si4O12 sheets oriented in the (0, 0, 1) direction and two MgO2 sheets oriented in the (0, 0, 1) direction. In each Mg3Si4O12 sheet, there are three inequivalent Mg sites. In the first Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with four SiO4 tetrahedra and edges with six MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.09–2.13 Å. In the second Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with four SiO4 tetrahedra and edges with six MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.01–2.20 Å. In the third Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with four SiO4 tetrahedra and edges with six MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.02–2.22 Å. There are four inequivalent Si sites. In the first Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with three MgO6 octahedra and corners with three equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 56–59°. There is one shorter (1.65 Å) and three longer (1.66 Å) Si–O bond length. In the second Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with three MgO6 octahedra and corners with three equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 56–59°. There is one shorter (1.65 Å) and three longer (1.66 Å) Si–O bond length. In the third Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with three MgO6 octahedra and corners with three equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 56–59°. There is one shorter (1.65 Å) and three longer (1.66 Å) Si–O bond length. In the fourth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with three MgO6 octahedra and corners with three equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 56–60°. There is one shorter (1.65 Å) and three longer (1.66 Å) Si–O bond length. There are twelve inequivalent O sites. In the first O site, O is bonded in a trigonal non-coplanar geometry to three Mg atoms. In the second O site, O is bonded in a trigonal non-coplanar geometry to three Mg atoms. In the third O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the fourth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the fifth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the sixth O site, O is bonded to three Mg and one Si atom to form a mixture of distorted corner and edge-sharing OMg3Si trigonal pyramids. In the seventh O site, O is bonded to three Mg and one Si atom to form a mixture of distorted corner and edge-sharing OMg3Si trigonal pyramids. In the eighth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the ninth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the tenth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the eleventh O site, O is bonded to three Mg and one Si atom to form a mixture of distorted corner and edge-sharing OMg3Si trigonal pyramids. In the twelfth O site, O is bonded to three Mg and one Si atom to form a mixture of distorted corner and edge-sharing OMg3Si trigonal pyramids. In each MgO2 sheet, there are three inequivalent Mg sites. In the first Mg site, Mg is bonded to six O atoms to form distorted edge-sharing MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 1.94–2.08 Å. In the second Mg site, Mg is bonded to six O atoms to form distorted edge-sharing MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 1.94–2.08 Å. In the third Mg site, Mg is bonded to six O atoms to form distorted edge-sharing MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 1.93–2.09 Å. There are six inequivalent O sites. In the first O site, O is bonded in a trigonal non-coplanar geometry to three Mg atoms. In the second O site, O is bonded in a trigonal non-coplanar geometry to three Mg atoms. In the third O site, O is bonded in a trigonal non-coplanar geometry to three Mg atoms. In the fourth O site, O is bonded in a trigonal non-coplanar geometry to three Mg atoms. In the fifth O site, O is bonded in a trigonal non-coplanar geometry to three Mg atoms. In the sixth O site, O is bonded in a trigonal non-coplanar geometry to three Mg atoms.
(MgO2)3Mg3Si4O12 crystallizes in the monoclinic C2/c space group. The structure is two-dimensional and consists of two Mg3Si4O12 sheets oriented in the (0, 0, 1) direction and two MgO2 sheets oriented in the (0, 0, 1) direction. In each Mg3Si4O12 sheet, there are two inequivalent Mg sites. In the first Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with four SiO4 tetrahedra and edges with six MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.03–2.15 Å. In the second Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with four SiO4 tetrahedra and edges with six equivalent MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.07–2.17 Å. There are two inequivalent Si sites. In the first Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with three MgO6 octahedra and corners with three equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 56–59°. There are a spread of Si–O bond distances ranging from 1.64–1.66 Å. In the second Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with three MgO6 octahedra and corners with three equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 57–59°. There is two shorter (1.65 Å) and two longer (1.66 Å) Si–O bond length. There are six inequivalent O sites. In the first O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the second O site, O is bonded in a trigonal non-coplanar geometry to three Mg atoms. In the third O site, O is bonded in a distorted rectangular see-saw-like geometry to three Mg and one Si atom. In the fourth O site, O is bonded in a rectangular see-saw-like geometry to three Mg and one Si atom. In the fifth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the sixth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In each MgO2 sheet, there are two inequivalent Mg sites. In the first Mg site, Mg is bonded to six O atoms to form distorted edge-sharing MgO6 octahedra. There are two shorter (1.94 Å) and four longer (2.06 Å) Mg–O bond lengths. In the second Mg site, Mg is bonded to six O atoms to form distorted edge-sharing MgO6 octahedra. There are two shorter (1.95 Å) and four longer (2.06 Å) Mg–O bond lengths. There are three inequivalent O sites. In the first O site, O is bonded in a trigonal non-coplanar geometry to three Mg atoms. In the second O site, O is bonded in a trigonal non-coplanar geometry to three Mg atoms. In the third O site, O is bonded in a trigonal non-coplanar geometry to three Mg atoms.
Three competing bonding mechanisms have been identified for the alkaline-earth metal superoxides: these result in a change in the optimal structure and ground state as the alkaline-earth metal becomes heavier. For example, BeO2 has a linear 3Sigma(-)g ground-state structure, whereas both CaO2 and SrO2 have C(2v)1A1 structures. For MgO2, the theoretical calculations are less definitive, as the 3A2 C(2v) structure is computed to lie only about 3 kcal/mol above the 3Sigma(-)g linear structure. The bond dissociation energies for the alkaline-earth metal superoxides have been computed using extensive Gaussian basis sets and treating electron correlation at the modified coupled-pair functional or coupled-cluster singles and doubles level with a perturbational estimate of the triple excitations.