DOE OSTI2020
Na3LiBe2F8 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are three inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to seven F1- atoms to form distorted NaF7 pentagonal bipyramids that share corners with three BeF4 tetrahedra, corners with two equivalent LiF5 trigonal bipyramids, edges with two BeF4 tetrahedra, and an edgeedge with one LiF5 trigonal bipyramid. There are a spread of Na–F bond distances ranging from 2.33–2.62 Å. In the second Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six F1- atoms. There are a spread of Na–F bond distances ranging from 2.34–2.42 Å. In the third Na1+ site, Na1+ is bonded in a 5-coordinate geometry to seven F1- atoms. There are a spread of Na–F bond distances ranging from 2.31–2.86 Å. Li1+ is bonded to five F1- atoms to form distorted LiF5 trigonal bipyramids that share corners with two equivalent NaF7 pentagonal bipyramids, corners with three equivalent BeF4 tetrahedra, an edgeedge with one NaF7 pentagonal bipyramid, and an edgeedge with one BeF4 tetrahedra. There are a spread of Li–F bond distances ranging from 1.91–2.41 Å. There are two inequivalent Be2+ sites. In the first Be2+ site, Be2+ is bonded to four F1- atoms to form BeF4 tetrahedra that share corners with two equivalent NaF7 pentagonal bipyramids, an edgeedge with one NaF7 pentagonal bipyramid, and an edgeedge with one LiF5 trigonal bipyramid. There is two shorter (1.55 Å) and two longer (1.58 Å) Be–F bond length. In the second Be2+ site, Be2+ is bonded to four F1- atoms to form BeF4 tetrahedra that share a cornercorner with one NaF7 pentagonal bipyramid, corners with three equivalent LiF5 trigonal bipyramids, and an edgeedge with one NaF7 pentagonal bipyramid. There are a spread of Be–F bond distances ranging from 1.56–1.58 Å. There are eight inequivalent F1- sites. In the first F1- site, F1- is bonded in a distorted single-bond geometry to three Na1+, one Li1+, and one Be2+ atom. In the second F1- site, F1- is bonded in a 1-coordinate geometry to three Na1+ and one Be2+ atom. In the third F1- site, F1- is bonded in a 3-coordinate geometry to one Na1+, one Li1+, and one Be2+ atom. In the fourth F1- site, F1- is bonded in a 2-coordinate geometry to two Na1+, one Li1+, and one Be2+ atom. In the fifth F1- site, F1- is bonded in a 4-coordinate geometry to three Na1+ and one Be2+ atom. In the sixth F1- site, F1- is bonded in a 4-coordinate geometry to two Na1+, one Li1+, and one Be2+ atom. In the seventh F1- site, F1- is bonded in a 5-coordinate geometry to three Na1+, one Li1+, and one Be2+ atom. In the eighth F1- site, F1- is bonded in a distorted trigonal pyramidal geometry to three Na1+ and one Be2+ atom.