DOI: 10.17188/1268796
title: Materials Data on Na3TmSi2O7 by Materials Project

description: Na3TmSi2O7 crystallizes in the hexagonal P6_3 space group. The structure is three-dimensional. there are five inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to four O2- atoms to form distorted NaO4 tetrahedra that share a cornercorner with one TmO6 octahedra, a cornercorner with one TmO6 pentagonal pyramid, corners with two equivalent NaO4 tetrahedra, corners with four SiO4 tetrahedra, and an edgeedge with one TmO6 octahedra. The corner-sharing octahedral tilt angles are 76°. There are a spread of Na–O bond distances ranging from 2.32–2.53 Å. In the second Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are three shorter (2.58 Å) and three longer (2.59 Å) Na–O bond lengths. In the third Na1+ site, Na1+ is bonded to four O2- atoms to form distorted NaO4 tetrahedra that share a cornercorner with one TmO6 octahedra, a cornercorner with one TmO6 pentagonal pyramid, corners with two equivalent NaO4 tetrahedra, corners with four SiO4 tetrahedra, and an edgeedge with one TmO6 octahedra. The corner-sharing octahedral tilt angles are 76°. There are a spread of Na–O bond distances ranging from 2.33–2.47 Å. In the fourth Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are three shorter (2.51 Å) and three longer (2.53 Å) Na–O bond lengths. In the fifth Na1+ site, Na1+ is bonded in a distorted trigonal planar geometry to three equivalent O2- atoms. All Na–O bond lengths are 2.28 Å. There are three inequivalent Tm3+ sites. In the first Tm3+ site, Tm3+ is bonded to six O2- atoms to form TmO6 octahedra that share corners with three equivalent NaO4 tetrahedra, corners with six SiO4 tetrahedra, and edges with three equivalent NaO4 tetrahedra. There are three shorter (2.22 Å) and three longer (2.23 Å) Tm–O bond lengths. In the second Tm3+ site, Tm3+ is bonded to six O2- atoms to form distorted TmO6 pentagonal pyramids that share corners with six NaO4 tetrahedra and corners with six SiO4 tetrahedra. All Tm–O bond lengths are 2.26 Å. In the third Tm3+ site, Tm3+ is bonded to six O2- atoms to form TmO6 octahedra that share corners with three equivalent NaO4 tetrahedra, corners with six SiO4 tetrahedra, and edges with three equivalent NaO4 tetrahedra. There are three shorter (2.22 Å) and three longer (2.24 Å) Tm–O bond lengths. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two TmO6 octahedra, a cornercorner with one TmO6 pentagonal pyramid, a cornercorner with one SiO4 tetrahedra, and corners with four NaO4 tetrahedra. The corner-sharing octahedra tilt angles range from 32–36°. There are a spread of Si–O bond distances ranging from 1.63–1.68 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two TmO6 octahedra, a cornercorner with one TmO6 pentagonal pyramid, a cornercorner with one SiO4 tetrahedra, and corners with four NaO4 tetrahedra. The corner-sharing octahedra tilt angles range from 30–37°. There are a spread of Si–O bond distances ranging from 1.63–1.69 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Tm3+, and one Si4+ atom. In the second O2- site, O2- is bonded in a 1-coordinate geometry to two Na1+, one Tm3+, and one Si4+ atom. In the third O2- site, O2- is bonded in a trigonal planar geometry to one Na1+ and two Si4+ atoms. In the fourth O2- site, O2- is bonded to two Na1+, one Tm3+, and one Si4+ atom to form distorted corner-sharing ONa2TmSi tetrahedra. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Tm3+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Tm3+, and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Tm3+, and one Si4+ atom.