SEARCH · Engineering Papers
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
NaAlSe2 crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. Na1+ is bonded in a 8-coordinate geometry to eight equivalent Se2- atoms. All Na–Se bond lengths are 3.28 Å. Al3+ is bonded to four equivalent Se2- atoms to form edge-sharing AlSe4 tetrahedra. All Al–Se bond lengths are 2.43 Å. Se2- is bonded in a 2-coordinate geometry to four equivalent Na1+ and two equivalent Al3+ atoms.
NaAlSe2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to six Se2- atoms to form distorted NaSe6 pentagonal pyramids that share corners with ten AlSe4 tetrahedra, edges with two equivalent NaSe6 pentagonal pyramids, an edgeedge with one AlSe4 tetrahedra, and faces with three NaSe6 pentagonal pyramids. There are a spread of Na–Se bond distances ranging from 3.02–3.21 Å. In the second Na1+ site, Na1+ is bonded to six Se2- atoms to form distorted NaSe6 pentagonal pyramids that share corners with four equivalent NaSe6 pentagonal pyramids, corners with six AlSe4 tetrahedra, edges with two equivalent NaSe6 pentagonal pyramids, edges with three AlSe4 tetrahedra, and faces with two equivalent NaSe6 pentagonal pyramids. There are a spread of Na–Se bond distances ranging from 3.10–3.22 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four Se2- atoms to form AlSe4 tetrahedra that share corners with eight NaSe6 pentagonal pyramids, corners with four AlSe4 tetrahedra, and edges with two NaSe6 pentagonal pyramids. There are one shorter (2.40 Å) and three longer (2.41 Å) Al–Se bond lengths. In the second Al3+ site, Al3+ is bonded to four Se2- atoms to form AlSe4 tetrahedra that share corners with eight NaSe6 pentagonal pyramids, corners with four AlSe4 tetrahedra, and edges with two equivalent NaSe6 pentagonal pyramids. There are one shorter (2.40 Å) and three longer (2.41 Å) Al–Se bond lengths. There are five inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 2-coordinate geometry to four Na1+ and two equivalent Al3+ atoms. In the second Se2- site, Se2- is bonded in a 2-coordinate geometry to four Na1+ and two equivalent Al3+ atoms. In the third Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to two Na1+ and two Al3+ atoms. In the fourth Se2- site, Se2- is bonded in a 2-coordinate geometry to four Na1+ and two Al3+ atoms. In the fifth Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to two Na1+ and two Al3+ atoms.
Na3AlSe3 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 in a 6-coordinate geometry to six Se2- atoms. There are a spread of Na–Se bond distances ranging from 2.95–3.59 Å. In the second Na1+ site, Na1+ is bonded in a 4-coordinate geometry to six Se2- atoms. There are a spread of Na–Se bond distances ranging from 2.91–3.51 Å. In the third Na1+ site, Na1+ is bonded to six Se2- atoms to form distorted NaSe6 octahedra that share corners with two equivalent NaSe6 octahedra, corners with four equivalent AlSe4 tetrahedra, edges with two equivalent NaSe6 octahedra, and edges with two equivalent AlSe4 tetrahedra. The corner-sharing octahedral tilt angles are 54°. There are a spread of Na–Se bond distances ranging from 3.00–3.63 Å. Al3+ is bonded to four Se2- atoms to form AlSe4 tetrahedra that share corners with four equivalent NaSe6 octahedra, edges with two equivalent NaSe6 octahedra, and an edgeedge with one AlSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 17–54°. There are a spread of Al–Se bond distances ranging from 2.37–2.46 Å. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to six Na1+ and two equivalent Al3+ atoms. In the second Se2- site, Se2- is bonded in a 7-coordinate geometry to six Na1+ and one Al3+ atom. In the third Se2- site, Se2- is bonded in a 7-coordinate geometry to six Na1+ and one Al3+ atom.