DOI: 10.17188/1282737
title: Materials Data on FeCoAs by Materials Project

description: FeCoAs crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are six inequivalent Fe2+ sites. In the first Fe2+ site, Fe2+ is bonded to five As3- atoms to form distorted FeAs5 trigonal bipyramids that share corners with three equivalent FeAs5 square pyramids, corners with two equivalent FeAs4 tetrahedra, corners with four CoAs4 tetrahedra, corners with two equivalent CoAs5 trigonal bipyramids, corners with five FeAs5 trigonal bipyramids, an edgeedge with one FeAs5 square pyramid, edges with six CoAs4 tetrahedra, an edgeedge with one CoAs5 trigonal bipyramid, and edges with four FeAs5 trigonal bipyramids. There are a spread of Fe–As bond distances ranging from 2.43–2.57 Å. In the second Fe2+ site, Fe2+ is bonded to five As3- atoms to form distorted FeAs5 trigonal bipyramids that share corners with three equivalent FeAs5 square pyramids, corners with two equivalent FeAs4 tetrahedra, corners with four CoAs4 tetrahedra, corners with two equivalent CoAs5 trigonal bipyramids, corners with five FeAs5 trigonal bipyramids, an edgeedge with one FeAs5 square pyramid, edges with six CoAs4 tetrahedra, an edgeedge with one CoAs5 trigonal bipyramid, and edges with four FeAs5 trigonal bipyramids. There are a spread of Fe–As bond distances ranging from 2.43–2.57 Å. In the third Fe2+ site, Fe2+ is bonded to five As3- atoms to form distorted FeAs5 square pyramids that share corners with six CoAs4 tetrahedra, corners with ten FeAs5 trigonal bipyramids, edges with two equivalent FeAs5 square pyramids, edges with six CoAs4 tetrahedra, and edges with four FeAs5 trigonal bipyramids. There are a spread of Fe–As bond distances ranging from 2.43–2.56 Å. In the fourth Fe2+ site, Fe2+ is bonded to five As3- atoms to form distorted FeAs5 trigonal bipyramids that share corners with two equivalent FeAs5 square pyramids, corners with six CoAs4 tetrahedra, corners with three equivalent CoAs5 trigonal bipyramids, corners with five FeAs5 trigonal bipyramids, an edgeedge with one FeAs5 square pyramid, edges with two equivalent FeAs4 tetrahedra, edges with four CoAs4 tetrahedra, an edgeedge with one CoAs5 trigonal bipyramid, and edges with four FeAs5 trigonal bipyramids. There are a spread of Fe–As bond distances ranging from 2.42–2.58 Å. In the fifth Fe2+ site, Fe2+ is bonded to five As3- atoms to form distorted FeAs5 trigonal bipyramids that share corners with two equivalent FeAs5 square pyramids, corners with six CoAs4 tetrahedra, corners with three equivalent CoAs5 trigonal bipyramids, corners with five FeAs5 trigonal bipyramids, an edgeedge with one FeAs5 square pyramid, edges with two equivalent FeAs4 tetrahedra, edges with four CoAs4 tetrahedra, an edgeedge with one CoAs5 trigonal bipyramid, and edges with four FeAs5 trigonal bipyramids. There are a spread of Fe–As bond distances ranging from 2.41–2.59 Å. In the sixth Fe2+ site, Fe2+ is bonded to four As3- atoms to form FeAs4 tetrahedra that share corners with two equivalent FeAs4 tetrahedra, corners with eight CoAs4 tetrahedra, corners with two equivalent CoAs5 trigonal bipyramids, corners with four FeAs5 trigonal bipyramids, edges with two CoAs4 tetrahedra, edges with two equivalent CoAs5 trigonal bipyramids, and edges with four FeAs5 trigonal bipyramids. There are a spread of Fe–As bond distances ranging from 2.27–2.36 Å. There are six inequivalent Co1+ sites. In the first Co1+ site, Co1+ is bonded to four As3- atoms to form CoAs4 tetrahedra that share a cornercorner with one FeAs4 tetrahedra, corners with nine CoAs4 tetrahedra, corners with two equivalent CoAs5 trigonal bipyramids, corners with four FeAs5 trigonal bipyramids, edges with two equivalent FeAs5 square pyramids, edges with two CoAs4 tetrahedra, and edges with four FeAs5 trigonal bipyramids. There are two shorter (2.27 Å) and two longer (2.36 Å) Co–As bond lengths. In the second Co1+ site, Co1+ is bonded to five As3- atoms to form distorted CoAs5 trigonal bipyramids that share corners with two equivalent FeAs4 tetrahedra, corners with four CoAs4 tetrahedra, corners with ten FeAs5 trigonal bipyramids, edges with two equivalent FeAs4 tetrahedra, edges with four CoAs4 tetrahedra, edges with two equivalent CoAs5 trigonal bipyramids, and edges with four FeAs5 trigonal bipyramids. There are a spread of Co–As bond distances ranging from 2.41–2.56 Å. In the third Co1+ site, Co1+ is bonded to four As3- atoms to form CoAs4 tetrahedra that share corners with two equivalent FeAs5 square pyramids, corners with ten CoAs4 tetrahedra, corners with four FeAs5 trigonal bipyramids, edges with two equivalent FeAs5 square pyramids, edges with two CoAs4 tetrahedra, and edges with four FeAs5 trigonal bipyramids. There are two shorter (2.27 Å) and two longer (2.37 Å) Co–As bond lengths. In the fourth Co1+ site, Co1+ is bonded to four As3- atoms to form CoAs4 tetrahedra that share corners with two equivalent FeAs5 square pyramids, corners with three equivalent FeAs4 tetrahedra, corners with seven CoAs4 tetrahedra, corners with four FeAs5 trigonal bipyramids, an edgeedge with one FeAs4 tetrahedra, an edgeedge with one CoAs4 tetrahedra, edges with two equivalent CoAs5 trigonal bipyramids, and edges with four FeAs5 trigonal bipyramids. There are a spread of Co–As bond distances ranging from 2.26–2.36 Å. In the fifth Co1+ site, Co1+ is bonded to four As3- atoms to form CoAs4 tetrahedra that share corners with two equivalent FeAs5 square pyramids, corners with three equivalent FeAs4 tetrahedra, corners with seven CoAs4 tetrahedra, corners with four FeAs5 trigonal bipyramids, an edgeedge with one FeAs4 tetrahedra, an edgeedge with one CoAs4 tetrahedra, edges with two equivalent CoAs5 trigonal bipyramids, and edges with four FeAs5 trigonal bipyramids. There are a spread of Co–As bond distances ranging from 2.26–2.36 Å. In the sixth Co1+ site, Co1+ is bonded to four As3- atoms to form CoAs4 tetrahedra that share a cornercorner with one FeAs4 tetrahedra, corners with nine CoAs4 tetrahedra, corners with two equivalent CoAs5 trigonal bipyramids, corners with four FeAs5 trigonal bipyramids, edges with two equivalent FeAs5 square pyramids, edges with two CoAs4 tetrahedra, and edges with four FeAs5 trigonal bipyramids. There are two shorter (2.27 Å) and two longer (2.36 Å) Co–As bond lengths. There are six inequivalent As3- sites. In the first As3- site, As3- is bonded in a 9-coordinate geometry to four Fe2+ and five Co1+ atoms. In the second As3- site, As3- is bonded in a 9-coordinate geometry to five Fe2+ and four Co1+ atoms. In the third As3- site, As3- is bonded in a 9-coordinate geometry to six Fe2+ and three Co1+ atoms. In the fourth As3- site, As3- is bonded in a 9-coordinate geometry to six Fe2+ and three Co1+ atoms. In the fifth As3- site, As3- is bonded in a 9-coordinate geometry to three Fe2+ and six Co1+ atoms. In the sixth As3- site, As3- is bonded in a 9-coordinate geometry to five Fe2+ and four Co1+ atoms.