Nd3Pd20Si6 crystallizes in the cubic Fm-3m space group. There are two inequivalent Nd sites. In the first Nd site, Nd(1) is bonded to four equivalent Pd(2) and twelve equivalent Pd(1) atoms to form distorted NdPd16 tetrahedra that share edges with six equivalent Nd(1)Pd16 tetrahedra and faces with four equivalent Nd(2)Pd12 cuboctahedra. In the second Nd site, Nd(2) is bonded to twelve equivalent Pd(1) atoms to form distorted face-sharing NdPd12 cuboctahedra. There are two inequivalent Pd sites. In the first Pd site, Pd(1) is bonded in a 2-coordinate geometry to one Nd(2), two equivalent Nd(1), and two equivalent Si(1) atoms. In the second Pd site, Pd(2) is bonded to one Nd(1) and three equivalent Si(1) atoms to form a mixture of edge and corner-sharing PdNdSi3 tetrahedra. Si(1) is bonded in a 8-coordinate geometry to four equivalent Pd(1) and four equivalent Pd(2) atoms.
Nd3Pd20Si6 crystallizes in the cubic Fm-3m space group. There are two inequivalent Nd sites. In the first Nd site, Nd(1) is bonded to four equivalent Pd(2) and twelve equivalent Pd(1) atoms to form distorted NdPd16 tetrahedra that share edges with six equivalent Nd(1)Pd16 tetrahedra and faces with four equivalent Nd(2)Pd12 cuboctahedra. All Nd(1)-Pd(2) bond lengths are 2.89 Å. All Nd(1)-Pd(1) bond lengths are 3.35 Å. In the second Nd site, Nd(2) is bonded to twelve equivalent Pd(1) atoms to form distorted face-sharing NdPd12 cuboctahedra. All Nd(2)-Pd(1) bond lengths are 3.02 Å. There are two inequivalent Pd sites. In the first Pd site, Pd(1) is bonded in a 2-coordinate geometry to one Nd(2), two equivalent Nd(1), and two equivalent Si(1) atoms. Both Pd(1)-Si(1) bond lengths are 2.43 Å. In the second Pd site, Pd(2) is bonded to one Nd(1) and three equivalent Si(1) atoms to form a mixture of edge and corner-sharing PdNdSi3 tetrahedra. All Pd(2)-Si(1) bond lengths are 2.47 Å. Si(1) is bonded in a 8-coordinate geometry to four equivalent Pd(1) and four equivalent Pd(2) atoms.