Er15Si9C crystallizes in the hexagonal P6_3mc space group. There are four inequivalent Er sites. In the first Er site, Er(1) is bonded in a 6-coordinate geometry to two equivalent Si(1), two equivalent Si(2), and two equivalent Si(3) atoms. In the second Er site, Er(2) is bonded in a 1-coordinate geometry to two equivalent Si(2), two equivalent Si(3), and one C(1) atom. In the third Er site, Er(3) is bonded in a 1-coordinate geometry to one Si(1), two equivalent Si(2), two equivalent Si(3), and one C(1) atom. In the fourth Er site, Er(4) is bonded in a 5-coordinate geometry to one Si(3) and four equivalent Si(1) atoms. There are three inequivalent Si sites. In the first Si site, Si(2) is bonded in a 8-coordinate geometry to two equivalent Er(2), two equivalent Er(3), and four equivalent Er(1) atoms. In the second Si site, Si(3) is bonded in a 9-coordinate geometry to one Er(4), two equivalent Er(2), two equivalent Er(3), and four equivalent Er(1) atoms. In the third Si site, Si(1) is bonded in a 9-coordinate geometry to one Er(3), four equivalent Er(1), and four equivalent Er(4) atoms. C(1) is bonded in an octahedral geometry to three equivalent Er(2) and three equivalent Er(3) atoms.
Er15Si9C crystallizes in the hexagonal P6_3mc space group. There are four inequivalent Er sites. In the first Er site, Er(1) is bonded in a 6-coordinate geometry to two equivalent Si(1), two equivalent Si(2), and two equivalent Si(3) atoms. There is one shorter (3.01 Å) and one longer (3.04 Å) Er(1)-Si(1) bond length. Both Er(1)-Si(2) bond lengths are 3.00 Å. There is one shorter (2.98 Å) and one longer (3.04 Å) Er(1)-Si(3) bond length. In the second Er site, Er(2) is bonded in a 1-coordinate geometry to two equivalent Si(2), two equivalent Si(3), and one C(1) atom. There is one shorter (3.05 Å) and one longer (3.15 Å) Er(2)-Si(2) bond length. Both Er(2)-Si(3) bond lengths are 2.93 Å. The Er(2)-C(1) bond length is 2.44 Å. In the third Er site, Er(3) is bonded in a 1-coordinate geometry to one Si(1), two equivalent Si(2), two equivalent Si(3), and one C(1) atom. The Er(3)-Si(1) bond length is 3.06 Å. Both Er(3)-Si(2) bond lengths are 2.93 Å. There is one shorter (3.21 Å) and one longer (3.64 Å) Er(3)-Si(3) bond length. The Er(3)-C(1) bond length is 2.44 Å. In the fourth Er site, Er(4) is bonded in a 5-coordinate geometry to one Si(3) and four equivalent Si(1) atoms. The Er(4)-Si(3) bond length is 2.99 Å. There are a spread of Er(4)-Si(1) bond distances ranging from 2.91-3.53 Å. There are three inequivalent Si sites. In the first Si site, Si(2) is bonded in a 8-coordinate geometry to two equivalent Er(2), two equivalent Er(3), and four equivalent Er(1) atoms. In the second Si site, Si(3) is bonded in a 9-coordinate geometry to one Er(4), two equivalent Er(2), two equivalent Er(3), and four equivalent Er(1) atoms. In the third Si site, Si(1) is bonded in a 9-coordinate geometry to one Er(3), four equivalent Er(1), and four equivalent Er(4) atoms. C(1) is bonded in an octahedral geometry to three equivalent Er(2) and three equivalent Er(3) atoms.