Materials Data on Na2Al2B2O7 by Materials Project

Abstract

Na2Al2B2O7 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to six O2- atoms to form NaO6 octahedra that share corners with six equivalent AlO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.41–2.51 Å. In the second Na1+ site, Na1+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Na–O bond distances ranging from 2.64–2.97 Å. Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent NaO6 octahedra and a cornercorner with one AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 66–68°. There is one shorter (1.74 Å) and three longer (1.77 Å) Al–O bond length. B3+ is bonded in a trigonal planar geometry to three O2- atoms. There is one shorter (1.38 Å) and two longer (1.39 Å) B–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted linear geometry to three equivalent Na1+ and two equivalent Al3+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two Na1+, one Al3+, and one B3+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to two Na1+, one Al3+, and one B3+ atom. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Al3+, and one B3+ atom.