Materials Data on KFeSe2 by Materials Project
KFeSe2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. K1+ is bonded to eight equivalent Se2- atoms to form distorted KSe8 hexagonal bipyramids that share corners with four equivalent KSe8 hexagonal bipyramids, corners with six equivalent FeSe4 tetrahedra, edges with six equivalent KSe8 hexagonal bipyramids, edges with five equivalent FeSe4 tetrahedra, and faces with two equivalent KSe8 hexagonal bipyramids. There are a spread of K–Se bond distances ranging from 3.49–3.59 Å. Fe3+ is bonded to four equivalent Se2- atoms to form FeSe4 tetrahedra that share corners with six equivalent KSe8 hexagonal bipyramids, edges with five equivalent KSe8 hexagonal bipyramids, and edges with two equivalent FeSe4 tetrahedra. There are two shorter (2.33 Å) and two longer (2.35 Å) Fe–Se bond lengths. Se2- is bonded in a 6-coordinate geometry to four equivalent K1+ and two equivalent Fe3+ atoms.