Materials Data on Na2Al2B2O7 by Materials Project
Na2Al2B2O7 crystallizes in the trigonal P-31c space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a distorted q6 geometry to nine O2- atoms. There are three shorter (2.81 Å) and six longer (2.92 Å) Na–O bond lengths. In the second Na1+ site, Na1+ is bonded to six equivalent O2- atoms to form NaO6 octahedra that share corners with six equivalent AlO4 tetrahedra. All Na–O bond lengths are 2.45 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 octahedral tilt angles are 66°. There is one shorter (1.73 Å) and three longer (1.77 Å) Al–O bond length. B3+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All B–O bond lengths are 1.38 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to two Na1+, one Al3+, and one B3+ atom. In the second O2- site, O2- is bonded in a distorted linear geometry to three equivalent Na1+ and two equivalent Al3+ atoms.