Nd15Ni2Si7 crystallizes in the orthorhombic Fmm2 space group. There are eleven inequivalent Nd sites. In the first Nd site, Nd(1) is bonded to one Ni(2), one Ni(3), two equivalent Si(1), and two equivalent Si(4) atoms to form distorted NdSi4Ni2 octahedra that share corners with four equivalent Nd(1)Si4Ni2 octahedra, corners with two equivalent Nd(3)Si4Ni trigonal bipyramids, corners with two equivalent Nd(4)Si4Ni trigonal bipyramids, corners with two equivalent Nd(7)Si4Ni trigonal bipyramids, corners with two equivalent Nd(6)Si5 trigonal bipyramids, corners with four equivalent Nd(9)Si4Ni trigonal bipyramids, faces with two equivalent Nd(4)Si4Ni trigonal bipyramids, and faces with two equivalent Nd(7)Si4Ni trigonal bipyramids. The corner-sharing octahedral tilt angles range from 55-56°. In the second Nd site, Nd(2) is bonded in a 6-coordinate geometry to one Ni(1), one Si(1), one Si(2), one Si(3), and two equivalent Si(5) atoms. In the third Nd site, Nd(3) is bonded to one Ni(1), two equivalent Si(1), and two equivalent Si(5) atoms to form distorted NdSi4Ni trigonal bipyramids that share corners with two equivalent Nd(1)Si4Ni2 octahedra, corners with two equivalent Nd(4)Si4Ni trigonal bipyramids, corners with two equivalent Nd(6)Si5 trigonal bipyramids, corners with four equivalent Nd(11)Si4Ni trigonal bipyramids,  an edgeedge with one Nd(7)Si4Ni trigonal bipyramid,  an edgeedge with one Nd(6)Si5 trigonal bipyramid,  an edgeedge with one Nd(8)Si5 trigonal bipyramid, edges with four equivalent Nd(9)Si4Ni trigonal bipyramids, and  a faceface with one Nd(5)Si4Ni trigonal bipyramid. The corner-sharing octahedral tilt angles are 63°. In the fourth Nd site, Nd(4) is bonded to one Ni(2), two equivalent Si(1), and two equivalent Si(4) atoms to form distorted NdSi4Ni trigonal bipyramids that share corners with two equivalent Nd(1)Si4Ni2 octahedra, corners with two equivalent Nd(3)Si4Ni trigonal bipyramids, corners with two equivalent Nd(7)Si4Ni trigonal bipyramids, corners with four equivalent Nd(9)Si4Ni trigonal bipyramids,  an edgeedge with one Nd(6)Si5 trigonal bipyramid, edges with two equivalent Nd(7)Si4Ni trigonal bipyramids, faces with two equivalent Nd(1)Si4Ni2 octahedra, and  a faceface with one Nd(4)Si4Ni trigonal bipyramid. The corner-sharing octahedral tilt angles are 42°. In the fifth Nd site, Nd(5) is bonded to one Ni(1), two equivalent Si(2), and two equivalent Si(5) atoms to form distorted NdSi4Ni trigonal bipyramids that share corners with two equivalent Nd(5)Si4Ni trigonal bipyramids, corners with two equivalent Nd(8)Si5 trigonal bipyramids, corners with four equivalent Nd(11)Si4Ni trigonal bipyramids, corners with four equivalent Nd(9)Si4Ni trigonal bipyramids,  an edgeedge with one Nd(6)Si5 trigonal bipyramid, edges with two equivalent Nd(8)Si5 trigonal bipyramids, edges with four equivalent Nd(11)Si4Ni trigonal bipyramids, and  a faceface with one Nd(3)Si4Ni trigonal bipyramid. In the sixth Nd site, Nd(6) is bonded to one Si(3), two equivalent Si(1), and two equivalent Si(5) atoms to form distorted NdSi5 trigonal bipyramids that share corners with two equivalent Nd(1)Si4Ni2 octahedra, corners with two equivalent Nd(3)Si4Ni trigonal bipyramids, corners with two equivalent Nd(7)Si4Ni trigonal bipyramids, corners with four equivalent Nd(11)Si4Ni trigonal bipyramids,  an edgeedge with one Nd(3)Si4Ni trigonal bipyramid,  an edgeedge with one Nd(4)Si4Ni trigonal bipyramid,  an edgeedge with one Nd(5)Si4Ni trigonal bipyramid, edges with four equivalent Nd(9)Si4Ni trigonal bipyramids, and  a faceface with one Nd(8)Si5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 64°. In the seventh Nd site, Nd(7) is bonded to one Ni(3), two equivalent Si(1), and two equivalent Si(4) atoms to form distorted NdSi4Ni trigonal bipyramids that share corners with two equivalent Nd(1)Si4Ni2 octahedra, corners with two equivalent Nd(4)Si4Ni trigonal bipyramids, corners with two equivalent Nd(6)Si5 trigonal bipyramids, corners with four equivalent Nd(9)Si4Ni trigonal bipyramids,  an edgeedge with one Nd(3)Si4Ni trigonal bipyramid, edges with two equivalent Nd(4)Si4Ni trigonal bipyramids, faces with two equivalent Nd(1)Si4Ni2 octahedra, and  a faceface with one Nd(7)Si4Ni trigonal bipyramid. The corner-sharing octahedral tilt angles are 42°. In the eighth Nd site, Nd(8) is bonded to one Si(3), two equivalent Si(2), and two equivalent Si(5) atoms to form distorted NdSi5 trigonal bipyramids that share corners with two equivalent Nd(5)Si4Ni trigonal bipyramids, corners with two equivalent Nd(8)Si5 trigonal bipyramids, corners with four equivalent Nd(11)Si4Ni trigonal bipyramids, corners with four equivalent Nd(9)Si4Ni trigonal bipyramids,  an edgeedge with one Nd(3)Si4Ni trigonal bipyramid, edges with two equivalent Nd(5)Si4Ni trigonal bipyramids, edges with four equivalent Nd(11)Si4Ni trigonal bipyramids, and  a faceface with one Nd(6)Si5 trigonal bipyramid. In the ninth Nd site, Nd(9) is bonded to one Ni(1), one Si(3), one Si(5), and two equivalent Si(1) atoms to form distorted NdSi4Ni trigonal bipyramids that share corners with two equivalent Nd(1)Si4Ni2 octahedra, corners with two equivalent Nd(4)Si4Ni trigonal bipyramids, corners with two equivalent Nd(5)Si4Ni trigonal bipyramids, corners with two equivalent Nd(7)Si4Ni trigonal bipyramids, corners with two equivalent Nd(9)Si4Ni trigonal bipyramids, corners with two equivalent Nd(8)Si5 trigonal bipyramids,  an edgeedge with one Nd(11)Si4Ni trigonal bipyramid,  an edgeedge with one Nd(9)Si4Ni trigonal bipyramid, edges with two equivalent Nd(3)Si4Ni trigonal bipyramids, edges with two equivalent Nd(6)Si5 trigonal bipyramids, and  a faceface with one Nd(11)Si4Ni trigonal bipyramid. The corner-sharing octahedral tilt angles are 64°. In the tenth Nd site, Nd(10) is bonded in a 5-coordinate geometry to one Ni(2), one Ni(3), one Si(4), and two equivalent Si(1) atoms. In the eleventh Nd site, Nd(11) is bonded to one Ni(1), one Si(3), one Si(5), and two equivalent Si(2) atoms to form distorted NdSi4Ni trigonal bipyramids that share corners with two equivalent Nd(3)Si4Ni trigonal bipyramids, corners with two equivalent Nd(5)Si4Ni trigonal bipyramids, corners with two equivalent Nd(6)Si5 trigonal bipyramids, corners with two equivalent Nd(8)Si5 trigonal bipyramids, corners with four equivalent Nd(11)Si4Ni trigonal bipyramids,  an edgeedge with one Nd(9)Si4Ni trigonal bipyramid, edges with two equivalent Nd(11)Si4Ni trigonal bipyramids, edges with two equivalent Nd(5)Si4Ni trigonal bipyramids, edges with two equivalent Nd(8)Si5 trigonal bipyramids, and  a faceface with one Nd(9)Si4Ni trigonal bipyramid. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a 9-coordinate geometry to one Nd(3), one Nd(5), two equivalent Nd(11), two equivalent Nd(2), two equivalent Nd(9), and one Si(3) atom. In the second Ni site, Ni(2) is bonded in a 9-coordinate geometry to two equivalent Nd(1), two equivalent Nd(4), four equivalent Nd(10), and one Ni(3) atom. In the third Ni site, Ni(3) is bonded in a 9-coordinate geometry to two equivalent Nd(1), two equivalent Nd(7), four equivalent Nd(10), and one Ni(2) atom. There are five inequivalent Si sites. In the first Si site, Si(4) is bonded in a 9-coordinate geometry to two equivalent Nd(1), two equivalent Nd(10), two equivalent Nd(4), two equivalent Nd(7), and one Si(4) atom. In the second Si site, Si(5) is bonded in a 9-coordinate geometry to one Nd(11), one Nd(3), one Nd(5), one Nd(6), one Nd(8), one Nd(9), two equivalent Nd(2), and one Si(5) atom. In the third Si site, Si(1) is bonded in a 10-coordinate geometry to one Nd(1), one Nd(2), one Nd(3), one Nd(4), one Nd(6), one Nd(7), two equivalent Nd(10), and two equivalent Nd(9) atoms. In the fourth Si site, Si(2) is bonded in a 10-coordinate geometry to two equivalent Nd(2), two equivalent Nd(5), two equivalent Nd(8), and four equivalent Nd(11) atoms. In the fifth Si site, Si(3) is bonded in a 9-coordinate geometry to one Nd(6), one Nd(8), two equivalent Nd(11), two equivalent Nd(2), two equivalent Nd(9), and one Ni(1) atom.
Nd15Ni2Si7 crystallizes in the orthorhombic Fmm2 space group. There are eleven inequivalent Nd sites. In the first Nd site, Nd(1) is bonded to one Ni(2), one Ni(3), two equivalent Si(1), and two equivalent Si(4) atoms to form distorted NdSi4Ni2 octahedra that share corners with four equivalent Nd(1)Si4Ni2 octahedra, corners with two equivalent Nd(3)Si4Ni trigonal bipyramids, corners with two equivalent Nd(4)Si4Ni trigonal bipyramids, corners with two equivalent Nd(7)Si4Ni trigonal bipyramids, corners with two equivalent Nd(6)Si5 trigonal bipyramids, corners with four equivalent Nd(9)Si4Ni trigonal bipyramids, faces with two equivalent Nd(4)Si4Ni trigonal bipyramids, and faces with two equivalent Nd(7)Si4Ni trigonal bipyramids. The corner-sharing octahedral tilt angles range from 55-56°. The Nd(1)-Ni(2) bond length is 3.07 Å. The Nd(1)-Ni(3) bond length is 3.09 Å. Both Nd(1)-Si(1) bond lengths are 3.47 Å. There is one shorter (3.13 Å) and one longer (3.15 Å) Nd(1)-Si(4) bond length. In the second Nd site, Nd(2) is bonded in a 6-coordinate geometry to one Ni(1), one Si(1), one Si(2), one Si(3), and two equivalent Si(5) atoms. The Nd(2)-Ni(1) bond length is 3.03 Å. The Nd(2)-Si(1) bond length is 3.49 Å. The Nd(2)-Si(2) bond length is 3.50 Å. The Nd(2)-Si(3) bond length is 3.21 Å. There is one shorter (3.14 Å) and one longer (3.15 Å) Nd(2)-Si(5) bond length. In the third Nd site, Nd(3) is bonded to one Ni(1), two equivalent Si(1), and two equivalent Si(5) atoms to form distorted NdSi4Ni trigonal bipyramids that share corners with two equivalent Nd(1)Si4Ni2 octahedra, corners with two equivalent Nd(4)Si4Ni trigonal bipyramids, corners with two equivalent Nd(6)Si5 trigonal bipyramids, corners with four equivalent Nd(11)Si4Ni trigonal bipyramids,  an edgeedge with one Nd(7)Si4Ni trigonal bipyramid,  an edgeedge with one Nd(6)Si5 trigonal bipyramid,  an edgeedge with one Nd(8)Si5 trigonal bipyramid, edges with four equivalent Nd(9)Si4Ni trigonal bipyramids, and  a faceface with one Nd(5)Si4Ni trigonal bipyramid. The corner-sharing octahedral tilt angles are 63°. The Nd(3)-Ni(1) bond length is 3.20 Å. Both Nd(3)-Si(1) bond lengths are 3.19 Å. Both Nd(3)-Si(5) bond lengths are 3.10 Å. In the fourth Nd site, Nd(4) is bonded to one Ni(2), two equivalent Si(1), and two equivalent Si(4) atoms to form distorted NdSi4Ni trigonal bipyramids that share corners with two equivalent Nd(1)Si4Ni2 octahedra, corners with two equivalent Nd(3)Si4Ni trigonal bipyramids, corners with two equivalent Nd(7)Si4Ni trigonal bipyramids, corners with four equivalent Nd(9)Si4Ni trigonal bipyramids,  an edgeedge with one Nd(6)Si5 trigonal bipyramid, edges with two equivalent Nd(7)Si4Ni trigonal bipyramids, faces with two equivalent Nd(1)Si4Ni2 octahedra, and  a faceface with one Nd(4)Si4Ni trigonal bipyramid. The corner-sharing octahedral tilt angles are 42°. The Nd(4)-Ni(2) bond length is 3.06 Å. Both Nd(4)-Si(1) bond lengths are 3.18 Å. Both Nd(4)-Si(4) bond lengths are 3.09 Å. In the fifth Nd site, Nd(5) is bonded to one Ni(1), two equivalent Si(2), and two equivalent Si(5) atoms to form distorted NdSi4Ni trigonal bipyramids that share corners with two equivalent Nd(5)Si4Ni trigonal bipyramids, corners with two equivalent Nd(8)Si5 trigonal bipyramids, corners with four equivalent Nd(11)Si4Ni trigonal bipyramids, corners with four equivalent Nd(9)Si4Ni trigonal bipyramids,  an edgeedge with one Nd(6)Si5 trigonal bipyramid, edges with two equivalent Nd(8)Si5 trigonal bipyramids, edges with four equivalent Nd(11)Si4Ni trigonal bipyramids, and  a faceface with one Nd(3)Si4Ni trigonal bipyramid. The Nd(5)-Ni(1) bond length is 3.17 Å. Both Nd(5)-Si(2) bond lengths are 3.19 Å. Both Nd(5)-Si(5) bond lengths are 3.09 Å. In the sixth Nd site, Nd(6) is bonded to one Si(3), two equivalent Si(1), and two equivalent Si(5) atoms to form distorted NdSi5 trigonal bipyramids that share corners with two equivalent Nd(1)Si4Ni2 octahedra, corners with two equivalent Nd(3)Si4Ni trigonal bipyramids, corners with two equivalent Nd(7)Si4Ni trigonal bipyramids, corners with four equivalent Nd(11)Si4Ni trigonal bipyramids,  an edgeedge with one Nd(3)Si4Ni trigonal bipyramid,  an edgeedge with one Nd(4)Si4Ni trigonal bipyramid,  an edgeedge with one Nd(5)Si4Ni trigonal bipyramid, edges with four equivalent Nd(9)Si4Ni trigonal bipyramids, and  a faceface with one Nd(8)Si5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 64°. The Nd(6)-Si(3) bond length is 3.10 Å. Both Nd(6)-Si(1) bond lengths are 3.20 Å. Both Nd(6)-Si(5) bond lengths are 3.08 Å. In the seventh Nd site, Nd(7) is bonded to one Ni(3), two equivalent Si(1), and two equivalent Si(4) atoms to form distorted NdSi4Ni trigonal bipyramids that share corners with two equivalent Nd(1)Si4Ni2 octahedra, corners with two equivalent Nd(4)Si4Ni trigonal bipyramids, corners with two equivalent Nd(6)Si5 trigonal bipyramids, corners with four equivalent Nd(9)Si4Ni trigonal bipyramids,  an edgeedge with one Nd(3)Si4Ni trigonal bipyramid, edges with two equivalent Nd(4)Si4Ni trigonal bipyramids, faces with two equivalent Nd(1)Si4Ni2 octahedra, and  a faceface with one Nd(7)Si4Ni trigonal bipyramid. The corner-sharing octahedral tilt angles are 42°. The Nd(7)-Ni(3) bond length is 3.05 Å. Both Nd(7)-Si(1) bond lengths are 3.19 Å. Both Nd(7)-Si(4) bond lengths are 3.08 Å. In the eighth Nd site, Nd(8) is bonded to one Si(3), two equivalent Si(2), and two equivalent Si(5) atoms to form distorted NdSi5 trigonal bipyramids that share corners with two equivalent Nd(5)Si4Ni trigonal bipyramids, corners with two equivalent Nd(8)Si5 trigonal bipyramids, corners with four equivalent Nd(11)Si4Ni trigonal bipyramids, corners with four equivalent Nd(9)Si4Ni trigonal bipyramids,  an edgeedge with one Nd(3)Si4Ni trigonal bipyramid, edges with two equivalent Nd(5)Si4Ni trigonal bipyramids, edges with four equivalent Nd(11)Si4Ni trigonal bipyramids, and  a faceface with one Nd(6)Si5 trigonal bipyramid. The Nd(8)-Si(3) bond length is 3.07 Å. Both Nd(8)-Si(2) bond lengths are 3.19 Å. Both Nd(8)-Si(5) bond lengths are 3.07 Å. In the ninth Nd site, Nd(9) is bonded to one Ni(1), one Si(3), one Si(5), and two equivalent Si(1) atoms to form distorted NdSi4Ni trigonal bipyramids that share corners with two equivalent Nd(1)Si4Ni2 octahedra, corners with two equivalent Nd(4)Si4Ni trigonal bipyramids, corners with two equivalent Nd(5)Si4Ni trigonal bipyramids, corners with two equivalent Nd(7)Si4Ni trigonal bipyramids, corners with two equivalent Nd(9)Si4Ni trigonal bipyramids, corners with two equivalent Nd(8)Si5 trigonal bipyramids,  an edgeedge with one Nd(11)Si4Ni trigonal bipyramid,  an edgeedge with one Nd(9)Si4Ni trigonal bipyramid, edges with two equivalent Nd(3)Si4Ni trigonal bipyramids, edges with two equivalent Nd(6)Si5 trigonal bipyramids, and  a faceface with one Nd(11)Si4Ni trigonal bipyramid. The corner-sharing octahedral tilt angles are 64°. The Nd(9)-Ni(1) bond length is 3.05 Å. The Nd(9)-Si(3) bond length is 3.07 Å. The Nd(9)-Si(5) bond length is 3.12 Å. There is one shorter (3.21 Å) and one longer (3.25 Å) Nd(9)-Si(1) bond length. In the tenth Nd site, Nd(10) is bonded in a 5-coordinate geometry to one Ni(2), one Ni(3), one Si(4), and two equivalent Si(1) atoms. The Nd(10)-Ni(2) bond length is 2.98 Å. The Nd(10)-Ni(3) bond length is 2.97 Å. The Nd(10)-Si(4) bond length is 3.07 Å. There is one shorter (3.28 Å) and one longer (3.31 Å) Nd(10)-Si(1) bond length. In the eleventh Nd site, Nd(11) is bonded to one Ni(1), one Si(3), one Si(5), and two equivalent Si(2) atoms to form distorted NdSi4Ni trigonal bipyramids that share corners with two equivalent Nd(3)Si4Ni trigonal bipyramids, corners with two equivalent Nd(5)Si4Ni trigonal bipyramids, corners with two equivalent Nd(6)Si5 trigonal bipyramids, corners with two equivalent Nd(8)Si5 trigonal bipyramids, corners with four equivalent Nd(11)Si4Ni trigonal bipyramids,  an edgeedge with one Nd(9)Si4Ni trigonal bipyramid, edges with two equivalent Nd(11)Si4Ni trigonal bipyramids, edges with two equivalent Nd(5)Si4Ni trigonal bipyramids, edges with two equivalent Nd(8)Si5 trigonal bipyramids, and  a faceface with one Nd(9)Si4Ni trigonal bipyramid. The Nd(11)-Ni(1) bond length is 3.02 Å. The Nd(11)-Si(3) bond length is 3.06 Å. The Nd(11)-Si(5) bond length is 3.07 Å. There is one shorter (3.21 Å) and one longer (3.26 Å) Nd(11)-Si(2) bond length. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a 9-coordinate geometry to one Nd(3), one Nd(5), two equivalent Nd(11), two equivalent Nd(2), two equivalent Nd(9), and one Si(3) atom. The Ni(1)-Si(3) bond length is 2.49 Å. In the second Ni site, Ni(2) is bonded in a 9-coordinate geometry to two equivalent Nd(1), two equivalent Nd(4), four equivalent Nd(10), and one Ni(3) atom. The Ni(2)-Ni(3) bond length is 2.67 Å. In the third Ni site, Ni(3) is bonded in a 9-coordinate geometry to two equivalent Nd(1), two equivalent Nd(7), four equivalent Nd(10), and one Ni(2) atom. There are five inequivalent Si sites. In the first Si site, Si(4) is bonded in a 9-coordinate geometry to two equivalent Nd(1), two equivalent Nd(10), two equivalent Nd(4), two equivalent Nd(7), and one Si(4) atom. The Si(4)-Si(4) bond length is 2.50 Å. In the second Si site, Si(5) is bonded in a 9-coordinate geometry to one Nd(11), one Nd(3), one Nd(5), one Nd(6), one Nd(8), one Nd(9), two equivalent Nd(2), and one Si(5) atom. The Si(5)-Si(5) bond length is 2.50 Å. In the third Si site, Si(1) is bonded in a 10-coordinate geometry to one Nd(1), one Nd(2), one Nd(3), one Nd(4), one Nd(6), one Nd(7), two equivalent Nd(10), and two equivalent Nd(9) atoms. In the fourth Si site, Si(2) is bonded in a 10-coordinate geometry to two equivalent Nd(2), two equivalent Nd(5), two equivalent Nd(8), and four equivalent Nd(11) atoms. In the fifth Si site, Si(3) is bonded in a 9-coordinate geometry to one Nd(6), one Nd(8), two equivalent Nd(11), two equivalent Nd(2), two equivalent Nd(9), and one Ni(1) atom.