Er2Fe14Si3 crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 18-coordinate geometry to six equivalent Fe(2) and twelve equivalent Fe(3) atoms. In the second Er site, Er(2) is bonded in a 20-coordinate geometry to two equivalent Fe(1), six equivalent Fe(2), six equivalent Fe(3), and six equivalent Si(1) atoms. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 14-coordinate geometry to one Er(2), one Fe(1), three equivalent Fe(3), six equivalent Fe(2), and three equivalent Si(1) atoms. In the second Fe site, Fe(2) is bonded in a 12-coordinate geometry to one Er(1), one Er(2), two equivalent Fe(1), two equivalent Fe(2), four equivalent Fe(3), and two equivalent Si(1) atoms. In the third Fe site, Fe(3) is bonded to one Er(2), two equivalent Er(1), one Fe(1), two equivalent Fe(3), four equivalent Fe(2), and two equivalent Si(1) atoms to form distorted FeEr3Fe7Si2 cuboctahedra that share corners with five equivalent Si(1)Er2Fe10 cuboctahedra, corners with ten equivalent Fe(3)Er3Fe7Si2 cuboctahedra, edges with three equivalent Si(1)Er2Fe10 cuboctahedra, edges with five equivalent Fe(3)Er3Fe7Si2 cuboctahedra, faces with two equivalent Si(1)Er2Fe10 cuboctahedra, and faces with eight equivalent Fe(3)Er3Fe7Si2 cuboctahedra. Si(1) is bonded to two equivalent Er(2), two equivalent Fe(1), four equivalent Fe(2), and four equivalent Fe(3) atoms to form distorted SiEr2Fe10 cuboctahedra that share corners with four equivalent Si(1)Er2Fe10 cuboctahedra, corners with ten equivalent Fe(3)Er3Fe7Si2 cuboctahedra, edges with six equivalent Fe(3)Er3Fe7Si2 cuboctahedra, faces with four equivalent Fe(3)Er3Fe7Si2 cuboctahedra, and faces with six equivalent Si(1)Er2Fe10 cuboctahedra.
Er2Fe14Si3 crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 18-coordinate geometry to six equivalent Fe(2) and twelve equivalent Fe(3) atoms. All Er(1)-Fe(2) bond lengths are 2.86 Å. There are six shorter (3.10 Å) and six longer (3.24 Å) Er(1)-Fe(3) bond lengths. In the second Er site, Er(2) is bonded in a 20-coordinate geometry to two equivalent Fe(1), six equivalent Fe(2), six equivalent Fe(3), and six equivalent Si(1) atoms. Both Er(2)-Fe(1) bond lengths are 2.94 Å. All Er(2)-Fe(2) bond lengths are 2.90 Å. All Er(2)-Fe(3) bond lengths are 3.07 Å. All Er(2)-Si(1) bond lengths are 3.15 Å. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 14-coordinate geometry to one Er(2), one Fe(1), three equivalent Fe(3), six equivalent Fe(2), and three equivalent Si(1) atoms. The Fe(1)-Fe(1) bond length is 2.29 Å. All Fe(1)-Fe(3) bond lengths are 2.58 Å. All Fe(1)-Fe(2) bond lengths are 2.80 Å. All Fe(1)-Si(1) bond lengths are 2.56 Å. In the second Fe site, Fe(2) is bonded in a 12-coordinate geometry to one Er(1), one Er(2), two equivalent Fe(1), two equivalent Fe(2), four equivalent Fe(3), and two equivalent Si(1) atoms. There is one shorter (2.51 Å) and one longer (2.59 Å) Fe(2)-Fe(2) bond length. There are two shorter (2.50 Å) and two longer (2.51 Å) Fe(2)-Fe(3) bond lengths. Both Fe(2)-Si(1) bond lengths are 2.43 Å. In the third Fe site, Fe(3) is bonded to one Er(2), two equivalent Er(1), one Fe(1), two equivalent Fe(3), four equivalent Fe(2), and two equivalent Si(1) atoms to form distorted FeEr3Fe7Si2 cuboctahedra that share corners with five equivalent Si(1)Er2Fe10 cuboctahedra, corners with ten equivalent Fe(3)Er3Fe7Si2 cuboctahedra, edges with three equivalent Si(1)Er2Fe10 cuboctahedra, edges with five equivalent Fe(3)Er3Fe7Si2 cuboctahedra, faces with two equivalent Si(1)Er2Fe10 cuboctahedra, and faces with eight equivalent Fe(3)Er3Fe7Si2 cuboctahedra. Both Fe(3)-Fe(3) bond lengths are 2.43 Å. Both Fe(3)-Si(1) bond lengths are 2.39 Å. Si(1) is bonded to two equivalent Er(2), two equivalent Fe(1), four equivalent Fe(2), and four equivalent Fe(3) atoms to form distorted SiEr2Fe10 cuboctahedra that share corners with four equivalent Si(1)Er2Fe10 cuboctahedra, corners with ten equivalent Fe(3)Er3Fe7Si2 cuboctahedra, edges with six equivalent Fe(3)Er3Fe7Si2 cuboctahedra, faces with four equivalent Fe(3)Er3Fe7Si2 cuboctahedra, and faces with six equivalent Si(1)Er2Fe10 cuboctahedra.