Materials Data on NaMg2HSe2O7 by Materials Project
NaMg2HSe2O7 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Na1+ is bonded to four O2- atoms to form distorted NaO4 tetrahedra that share corners with five MgO6 octahedra. The corner-sharing octahedra tilt angles range from 63–79°. There are a spread of Na–O bond distances ranging from 2.31–2.40 Å. There are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent NaO4 tetrahedra and edges with four MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.04–2.17 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent NaO4 tetrahedra and edges with two equivalent MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.08–2.18 Å. H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. There are two inequivalent Se4+ sites. In the first Se4+ site, Se4+ is bonded in a trigonal non-coplanar geometry to three O2- atoms. There is one shorter (1.72 Å) and two longer (1.74 Å) Se–O bond length. In the second Se4+ site, Se4+ is bonded in a trigonal non-coplanar geometry to three O2- atoms. There is two shorter (1.73 Å) and one longer (1.76 Å) Se–O bond length. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Na1+, one Mg2+, and one Se4+ atom. In the second O2- site, O2- is bonded to one Na1+, two equivalent Mg2+, and one Se4+ atom to form distorted ONaMg2Se tetrahedra that share corners with four ONaMg2Se tetrahedra and an edgeedge with one OMg3H tetrahedra. In the third O2- site, O2- is bonded to three Mg2+ and one H1+ atom to form a mixture of distorted corner and edge-sharing OMg3H tetrahedra. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Na1+, one Mg2+, and one Se4+ atom. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Mg2+ and one Se4+ atom.