DOE OSTI2020
Na8BeAl4Si7(O12Br)2 crystallizes in the tetragonal P-4 space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to three O2- and one Br1- atom to form distorted NaBrO3 tetrahedra that share corners with two equivalent AlO4 tetrahedra, corners with three NaBrO3 tetrahedra, and corners with four SiO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.39–2.55 Å. The Na–Br bond length is 2.96 Å. In the second Na1+ site, Na1+ is bonded to three O2- and one Br1- atom to form distorted NaBrO3 tetrahedra that share a cornercorner with one BeO4 tetrahedra, corners with two equivalent AlO4 tetrahedra, corners with three NaBrO3 tetrahedra, and corners with three SiO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.37–2.53 Å. The Na–Br bond length is 3.09 Å. Be2+ is bonded to four equivalent O2- atoms to form BeO4 tetrahedra that share corners with four equivalent NaBrO3 tetrahedra and corners with four equivalent SiO4 tetrahedra. All Be–O bond lengths are 1.64 Å. Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four NaBrO3 tetrahedra and corners with four SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.74–1.76 Å. There are four inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four equivalent O2- atoms to form SiO4 tetrahedra that share corners with four equivalent NaBrO3 tetrahedra and corners with four equivalent SiO4 tetrahedra. All Si–O bond lengths are 1.63 Å. In the second Si4+ site, Si4+ is bonded to four equivalent O2- atoms to form SiO4 tetrahedra that share corners with four equivalent NaBrO3 tetrahedra and corners with four equivalent AlO4 tetrahedra. All Si–O bond lengths are 1.63 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one BeO4 tetrahedra, a cornercorner with one SiO4 tetrahedra, corners with two equivalent AlO4 tetrahedra, and corners with four NaBrO3 tetrahedra. There are a spread of Si–O bond distances ranging from 1.60–1.69 Å. In the fourth Si4+ site, Si4+ is bonded to four equivalent O2- atoms to form SiO4 tetrahedra that share corners with four equivalent NaBrO3 tetrahedra and corners with four equivalent AlO4 tetrahedra. All Si–O bond lengths are 1.63 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+, one Be2+, and one Si4+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+, one Al3+, and one Si4+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+, one Al3+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Al3+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Al3+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+ and two Si4+ atoms. Br1- is bonded in a tetrahedral geometry to four Na1+ atoms.