Materials Data on Na4Sr(Ge2O5)3 by Materials Project
Na4SrGe6O15 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Na–O bond distances ranging from 2.41–2.54 Å. In the second Na1+ site, Na1+ is bonded to six equivalent O2- atoms to form NaO6 octahedra that share corners with six equivalent GeO4 tetrahedra and faces with two equivalent NaO6 octahedra. All Na–O bond lengths are 2.49 Å. Sr2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are three shorter (2.60 Å) and six longer (2.61 Å) Sr–O bond lengths. There are two inequivalent Ge4+ sites. In the first Ge4+ site, Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with two equivalent NaO6 octahedra and corners with four equivalent GeO6 octahedra. The corner-sharing octahedra tilt angles range from 37–63°. There are a spread of Ge–O bond distances ranging from 1.75–1.83 Å. In the second Ge4+ site, Ge4+ is bonded to six O2- atoms to form GeO6 octahedra that share corners with four equivalent GeO4 tetrahedra and edges with two equivalent GeO6 octahedra. There are a spread of Ge–O bond distances ranging from 1.89–2.03 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, one Sr2+, and two Ge4+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three Ge4+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, one Sr2+, and two equivalent Ge4+ atoms. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to four Na1+ and one Ge4+ atom.