DOE OSTI2020
La4Ag2Se7 crystallizes in the monoclinic Pc space group. The structure is three-dimensional. there are four inequivalent La3+ sites. In the first La3+ site, La3+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of La–Se bond distances ranging from 3.04–3.52 Å. In the second La3+ site, La3+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of La–Se bond distances ranging from 2.98–3.47 Å. In the third La3+ site, La3+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of La–Se bond distances ranging from 3.04–3.46 Å. In the fourth La3+ site, La3+ is bonded to six Se2- atoms to form distorted LaSe6 pentagonal pyramids that share corners with two equivalent LaSe6 pentagonal pyramids, corners with four AgSe6 pentagonal pyramids, edges with two equivalent AgSe6 pentagonal pyramids, and faces with two equivalent AgSe6 pentagonal pyramids. There are a spread of La–Se bond distances ranging from 2.87–3.24 Å. There are two inequivalent Ag1+ sites. In the first Ag1+ site, Ag1+ is bonded to six Se2- atoms to form distorted AgSe6 pentagonal pyramids that share corners with two equivalent LaSe6 pentagonal pyramids, corners with four equivalent AgSe6 pentagonal pyramids, an edgeedge with one AgSe6 pentagonal pyramid, and edges with two equivalent LaSe6 pentagonal pyramids. There are a spread of Ag–Se bond distances ranging from 2.76–3.23 Å. In the second Ag1+ site, Ag1+ is bonded to six Se2- atoms to form distorted AgSe6 pentagonal pyramids that share corners with two equivalent LaSe6 pentagonal pyramids, corners with four equivalent AgSe6 pentagonal pyramids, edges with three AgSe6 pentagonal pyramids, and faces with two equivalent LaSe6 pentagonal pyramids. There are a spread of Ag–Se bond distances ranging from 2.75–3.36 Å. There are seven inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 6-coordinate geometry to five La3+ and one Ag1+ atom. In the second Se2- site, Se2- is bonded in a 6-coordinate geometry to four La3+ and two Ag1+ atoms. In the third Se2- site, Se2- is bonded in a 6-coordinate geometry to five La3+ and one Ag1+ atom. In the fourth Se2- site, Se2- is bonded in a 6-coordinate geometry to three La3+ and three Ag1+ atoms. In the fifth Se2- site, Se2- is bonded in a distorted octahedral geometry to four La3+ and two Ag1+ atoms. In the sixth Se2- site, Se2- is bonded in a 6-coordinate geometry to six La3+ atoms. In the seventh Se2- site, Se2- is bonded in a 6-coordinate geometry to three La3+ and three Ag1+ atoms.