Materials Data on Na2Ge2Se5 by Materials Project
Na2Ge2Se5 crystallizes in the orthorhombic Pna2_1 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 four equivalent NaSe6 pentagonal pyramids, corners with two equivalent GeSe4 tetrahedra, a cornercorner with one NaSe5 trigonal bipyramid, edges with three GeSe4 tetrahedra, and edges with four equivalent NaSe5 trigonal bipyramids. There are a spread of Na–Se bond distances ranging from 2.94–3.33 Å. In the second Na1+ site, Na1+ is bonded to five Se2- atoms to form distorted NaSe5 trigonal bipyramids that share a cornercorner with one NaSe6 pentagonal pyramid, corners with six GeSe4 tetrahedra, corners with four equivalent NaSe5 trigonal bipyramids, and edges with four equivalent NaSe6 pentagonal pyramids. There are a spread of Na–Se bond distances ranging from 3.00–3.28 Å. There are two inequivalent Ge4+ sites. In the first Ge4+ site, Ge4+ is bonded to four Se2- atoms to form GeSe4 tetrahedra that share corners with two equivalent NaSe6 pentagonal pyramids, corners with three equivalent GeSe4 tetrahedra, corners with three equivalent NaSe5 trigonal bipyramids, and an edgeedge with one NaSe6 pentagonal pyramid. There are a spread of Ge–Se bond distances ranging from 2.31–2.44 Å. In the second Ge4+ site, Ge4+ is bonded to four Se2- atoms to form GeSe4 tetrahedra that share corners with three equivalent GeSe4 tetrahedra, corners with three equivalent NaSe5 trigonal bipyramids, and edges with two equivalent NaSe6 pentagonal pyramids. There are a spread of Ge–Se bond distances ranging from 2.32–2.43 Å. There are five inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to four Na1+ and one Ge4+ atom to form a mixture of corner and edge-sharing SeNa4Ge trigonal bipyramids. In the second Se2- site, Se2- is bonded in a 3-coordinate geometry to one Na1+ and two Ge4+ atoms. In the third Se2- site, Se2- is bonded in a water-like geometry to two Ge4+ atoms. In the fourth Se2- site, Se2- is bonded in a 4-coordinate geometry to two Na1+ and two Ge4+ atoms. In the fifth Se2- site, Se2- is bonded to four Na1+ and one Ge4+ atom to form a mixture of distorted corner and edge-sharing SeNa4Ge trigonal bipyramids.