Materials Data on Na2FeCuF7 by Materials Project
Na2FeCuF7 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are three inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to eight F1- atoms to form distorted NaF8 hexagonal bipyramids that share corners with two equivalent FeF6 octahedra, edges with two equivalent FeF6 octahedra, and edges with four CuF6 octahedra. The corner-sharing octahedral tilt angles are 50°. There are a spread of Na–F bond distances ranging from 2.18–2.89 Å. In the second Na1+ site, Na1+ is bonded in a 8-coordinate geometry to eight F1- atoms. There are a spread of Na–F bond distances ranging from 2.45–2.88 Å. In the third Na1+ site, Na1+ is bonded in a 8-coordinate geometry to eight F1- atoms. There are a spread of Na–F bond distances ranging from 2.34–2.98 Å. There are two inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to six F1- atoms to form FeF6 octahedra that share corners with four CuF6 octahedra and edges with two equivalent NaF8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 44–51°. There are a spread of Fe–F bond distances ranging from 1.94–1.99 Å. In the second Fe3+ site, Fe3+ is bonded to six F1- atoms to form FeF6 octahedra that share corners with two equivalent NaF8 hexagonal bipyramids and corners with four CuF6 octahedra. The corner-sharing octahedra tilt angles range from 38–52°. There are a spread of Fe–F bond distances ranging from 1.95–1.98 Å. There are two inequivalent Cu2+ sites. In the first Cu2+ site, Cu2+ is bonded to six F1- atoms to form CuF6 octahedra that share corners with two equivalent CuF6 octahedra, corners with four FeF6 octahedra, and edges with two equivalent NaF8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 38–51°. There are a spread of Cu–F bond distances ranging from 1.92–2.22 Å. In the second Cu2+ site, Cu2+ is bonded to six F1- atoms to form CuF6 octahedra that share corners with two equivalent CuF6 octahedra, corners with four FeF6 octahedra, and edges with two equivalent NaF8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 39–52°. There are a spread of Cu–F bond distances ranging from 1.93–2.27 Å. There are seven inequivalent F1- sites. In the first F1- site, F1- is bonded in a 2-coordinate geometry to two equivalent Na1+, one Fe3+, and one Cu2+ atom. In the second F1- site, F1- is bonded in a 4-coordinate geometry to two Na1+, one Fe3+, and one Cu2+ atom. In the third F1- site, F1- is bonded to three Na1+ and one Fe3+ atom to form a mixture of distorted edge and corner-sharing FNa3Fe tetrahedra. In the fourth F1- site, F1- is bonded in a distorted bent 150 degrees geometry to two Na1+ and two Cu2+ atoms. In the fifth F1- site, F1- is bonded in a 4-coordinate geometry to two Na1+, one Fe3+, and one Cu2+ atom. In the sixth F1- site, F1- is bonded to three Na1+ and one Fe3+ atom to form a mixture of distorted edge and corner-sharing FNa3Fe tetrahedra. In the seventh F1- site, F1- is bonded in a 3-coordinate geometry to two Na1+, one Fe3+, and one Cu2+ atom.