DOE OSTI2020
Sm6Ni20As13 crystallizes in the hexagonal P-6 space group. The structure is three-dimensional. there are two inequivalent Sm2+ sites. In the first Sm2+ site, Sm2+ is bonded to six As3- atoms to form distorted SmAs6 pentagonal pyramids that share corners with four equivalent SmAs6 pentagonal pyramids, corners with two equivalent NiAs5 square pyramids, corners with twelve NiAs4 tetrahedra, edges with two equivalent SmAs6 pentagonal pyramids, edges with eight NiAs4 tetrahedra, and faces with two equivalent SmAs6 pentagonal pyramids. There are a spread of Sm–As bond distances ranging from 3.02–3.07 Å. In the second Sm2+ site, Sm2+ is bonded to six As3- atoms to form distorted SmAs6 pentagonal pyramids that share corners with four equivalent SmAs6 pentagonal pyramids, corners with two equivalent NiAs5 square pyramids, corners with twelve NiAs4 tetrahedra, edges with two equivalent SmAs6 pentagonal pyramids, an edgeedge with one NiAs5 square pyramid, edges with seven NiAs4 tetrahedra, and faces with two equivalent SmAs6 pentagonal pyramids. There are a spread of Sm–As bond distances ranging from 2.98–3.07 Å. There are eight inequivalent Ni+1.35+ sites. In the first Ni+1.35+ site, Ni+1.35+ is bonded to four As3- atoms to form NiAs4 tetrahedra that share corners with four SmAs6 pentagonal pyramids, corners with two equivalent NiAs5 square pyramids, corners with ten NiAs4 tetrahedra, an edgeedge with one SmAs6 pentagonal pyramid, edges with four equivalent NiAs5 square pyramids, and edges with three NiAs4 tetrahedra. There are a spread of Ni–As bond distances ranging from 2.27–2.45 Å. In the second Ni+1.35+ site, Ni+1.35+ is bonded in a trigonal planar geometry to three equivalent As3- atoms. All Ni–As bond lengths are 2.34 Å. In the third Ni+1.35+ site, Ni+1.35+ is bonded to five As3- atoms to form distorted NiAs5 square pyramids that share corners with four SmAs6 pentagonal pyramids, corners with four equivalent NiAs5 square pyramids, corners with eight NiAs4 tetrahedra, an edgeedge with one SmAs6 pentagonal pyramid, edges with four equivalent NiAs5 square pyramids, and edges with seven NiAs4 tetrahedra. There are a spread of Ni–As bond distances ranging from 2.42–2.78 Å. In the fourth Ni+1.35+ site, Ni+1.35+ is bonded in a trigonal planar geometry to three equivalent As3- atoms. All Ni–As bond lengths are 2.32 Å. In the fifth Ni+1.35+ site, Ni+1.35+ is bonded to four As3- atoms to form NiAs4 tetrahedra that share corners with six SmAs6 pentagonal pyramids, corners with two equivalent NiAs5 square pyramids, corners with five NiAs4 tetrahedra, edges with four SmAs6 pentagonal pyramids, and edges with four NiAs4 tetrahedra. There are three shorter (2.39 Å) and one longer (2.40 Å) Ni–As bond lengths. In the sixth Ni+1.35+ site, Ni+1.35+ is bonded to four As3- atoms to form NiAs4 tetrahedra that share corners with four SmAs6 pentagonal pyramids, corners with three equivalent NiAs5 square pyramids, corners with eight NiAs4 tetrahedra, edges with three SmAs6 pentagonal pyramids, an edgeedge with one NiAs5 square pyramid, and edges with four NiAs4 tetrahedra. There are a spread of Ni–As bond distances ranging from 2.40–2.46 Å. In the seventh Ni+1.35+ site, Ni+1.35+ is bonded to four As3- atoms to form NiAs4 tetrahedra that share corners with six SmAs6 pentagonal pyramids, a cornercorner with one NiAs5 square pyramid, corners with six NiAs4 tetrahedra, edges with four SmAs6 pentagonal pyramids, and edges with four NiAs4 tetrahedra. There are a spread of Ni–As bond distances ranging from 2.38–2.44 Å. In the eighth Ni+1.35+ site, Ni+1.35+ is bonded to four As3- atoms to form NiAs4 tetrahedra that share corners with four SmAs6 pentagonal pyramids, corners with eleven NiAs4 tetrahedra, edges with three SmAs6 pentagonal pyramids, edges with two equivalent NiAs5 square pyramids, and edges with three NiAs4 tetrahedra. There are a spread of Ni–As bond distances ranging from 2.38–2.43 Å. There are five inequivalent As3- sites. In the first As3- site, As3- is bonded in a 9-coordinate geometry to four equivalent Sm2+ and five Ni+1.35+ atoms. In the second As3- site, As3- is bonded in a 9-coordinate geometry to two equivalent Sm2+ and seven Ni+1.35+ atoms. In the third As3- site, As3- is bonded in a 9-coordinate geometry to nine Ni+1.35+ atoms. In the fourth As3- site, As3- is bonded in a 9-coordinate geometry to four equivalent Sm2+ and five Ni+1.35+ atoms. In the fifth As3- site, As3- is bonded in a 9-coordinate geometry to two equivalent Sm2+ and seven Ni+1.35+ atoms.