Materials Data on Na2Ca(Ge3O7)2 by Materials Project
Na2CaGe6O14 is Esseneite-like structured and crystallizes in the monoclinic C2 space group. The structure is three-dimensional. Na1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Na–O bond distances ranging from 2.46–2.90 Å. Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.44–2.79 Å. There are four 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 GeO6 octahedra and corners with two equivalent GeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 60–62°. There are a spread of Ge–O bond distances ranging from 1.77–1.80 Å. In the second Ge4+ site, Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with two equivalent GeO6 octahedra and corners with two equivalent GeO4 tetrahedra. The corner-sharing octahedral tilt angles are 61°. There is two shorter (1.77 Å) and two longer (1.81 Å) Ge–O bond length. In the third Ge4+ site, Ge4+ is bonded to six O2- atoms to form corner-sharing GeO6 octahedra. There are a spread of Ge–O bond distances ranging from 1.92–1.95 Å. In the fourth Ge4+ site, Ge4+ is bonded to four O2- atoms to form corner-sharing GeO4 tetrahedra. There are a spread of Ge–O bond distances ranging from 1.70–1.81 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one Na1+ and two Ge4+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one Na1+ and two Ge4+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+ and two Ge4+ atoms. In the fourth O2- site, O2- is bonded to two equivalent Na1+, one Ca2+, and one Ge4+ atom to form distorted corner-sharing ONa2CaGe tetrahedra. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+, one Ca2+, and two Ge4+ atoms. In the sixth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Na1+ and two Ge4+ atoms. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+, one Ca2+, and two Ge4+ atoms.