DOE OSTI2020
Na(VSe2)2 crystallizes in the monoclinic Pm space group. The structure is three-dimensional. Na1+ is bonded in a 6-coordinate geometry to six Se2- atoms. There are a spread of Na–Se bond distances ranging from 2.98–3.10 Å. There are two inequivalent V+3.50+ sites. In the first V+3.50+ site, V+3.50+ is bonded to six Se2- atoms to form edge-sharing VSe6 octahedra. There are a spread of V–Se bond distances ranging from 2.48–2.59 Å. In the second V+3.50+ site, V+3.50+ is bonded to six Se2- atoms to form edge-sharing VSe6 octahedra. There are a spread of V–Se bond distances ranging from 2.47–2.59 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to two equivalent Na1+ and three V+3.50+ atoms to form distorted SeNa2V3 square pyramids that share corners with five equivalent SeNa2V3 trigonal bipyramids, corners with four SeNaV3 trigonal pyramids, edges with two equivalent SeNa2V3 square pyramids, edges with two equivalent SeNa2V3 trigonal bipyramids, and edges with four SeNaV3 trigonal pyramids. In the second Se2- site, Se2- is bonded to one Na1+ and three V+3.50+ atoms to form distorted SeNaV3 trigonal pyramids that share corners with two equivalent SeNa2V3 square pyramids, corners with two equivalent SeNa2V3 trigonal bipyramids, corners with six SeNaV3 trigonal pyramids, edges with two equivalent SeNa2V3 square pyramids, edges with two equivalent SeNa2V3 trigonal bipyramids, and an edgeedge with one SeNaV3 trigonal pyramid. In the third Se2- site, Se2- is bonded to two equivalent Na1+ and three V+3.50+ atoms to form distorted SeNa2V3 trigonal bipyramids that share corners with five equivalent SeNa2V3 square pyramids, corners with four SeNaV3 trigonal pyramids, edges with two equivalent SeNa2V3 square pyramids, edges with two equivalent SeNa2V3 trigonal bipyramids, and edges with four SeNaV3 trigonal pyramids. In the fourth Se2- site, Se2- is bonded to one Na1+ and three V+3.50+ atoms to form distorted SeNaV3 trigonal pyramids that share corners with two equivalent SeNa2V3 square pyramids, corners with two equivalent SeNa2V3 trigonal bipyramids, corners with six SeNaV3 trigonal pyramids, edges with two equivalent SeNa2V3 square pyramids, edges with two equivalent SeNa2V3 trigonal bipyramids, and an edgeedge with one SeNaV3 trigonal pyramid.