DOE OSTI2020
Cs2MgO2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are four inequivalent Cs1+ sites. In the first Cs1+ site, Cs1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of Cs–O bond distances ranging from 2.93–3.20 Å. In the second Cs1+ site, Cs1+ is bonded to four O2- atoms to form distorted CsO4 trigonal pyramids that share a cornercorner with one MgO4 tetrahedra, corners with two equivalent CsO4 trigonal pyramids, and an edgeedge with one MgO4 tetrahedra. There are a spread of Cs–O bond distances ranging from 2.99–3.20 Å. In the third Cs1+ site, Cs1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of Cs–O bond distances ranging from 2.98–3.12 Å. In the fourth Cs1+ site, Cs1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of Cs–O bond distances ranging from 3.09–3.43 Å. There are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded in a distorted trigonal planar geometry to three O2- atoms. There is one shorter (1.90 Å) and two longer (1.96 Å) Mg–O bond length. In the second Mg2+ site, Mg2+ is bonded to four O2- atoms to form distorted MgO4 tetrahedra that share a cornercorner with one CsO4 trigonal pyramid, an edgeedge with one MgO4 tetrahedra, and an edgeedge with one CsO4 trigonal pyramid. There are a spread of Mg–O bond distances ranging from 2.01–2.05 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to five Cs1+ and one Mg2+ atom. In the second O2- site, O2- is bonded in a distorted L-shaped geometry to four Cs1+ and two equivalent Mg2+ atoms. In the third O2- site, O2- is bonded in a 2-coordinate geometry to three Cs1+ and two Mg2+ atoms. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to four Cs1+ and two Mg2+ atoms.