Mn2NiSi crystallizes in the tetragonal I-4m2 space group. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to four equivalent Mn(2), four equivalent Ni(1), and four equivalent Si(1) atoms to form MnMn4Si4Ni4 cuboctahedra that share corners with four equivalent Mn(1)Mn4Si4Ni4 cuboctahedra, corners with eight equivalent Ni(1)Mn8Si4 cuboctahedra, edges with eight equivalent Mn(1)Mn4Si4Ni4 cuboctahedra, edges with eight equivalent Mn(2)Mn4Si4Ni4 cuboctahedra, edges with eight equivalent Si(1)Mn8Ni4 cuboctahedra, faces with four equivalent Mn(1)Mn4Si4Ni4 cuboctahedra, faces with four equivalent Mn(2)Mn4Si4Ni4 cuboctahedra, faces with four equivalent Si(1)Mn8Ni4 cuboctahedra, and faces with six equivalent Ni(1)Mn8Si4 cuboctahedra. In the second Mn site, Mn(2) is bonded to four equivalent Mn(1), four equivalent Ni(1), and four equivalent Si(1) atoms to form MnMn4Si4Ni4 cuboctahedra that share corners with four equivalent Mn(2)Mn4Si4Ni4 cuboctahedra, corners with eight equivalent Si(1)Mn8Ni4 cuboctahedra, edges with eight equivalent Mn(1)Mn4Si4Ni4 cuboctahedra, edges with eight equivalent Mn(2)Mn4Si4Ni4 cuboctahedra, edges with eight equivalent Ni(1)Mn8Si4 cuboctahedra, faces with four equivalent Mn(1)Mn4Si4Ni4 cuboctahedra, faces with four equivalent Mn(2)Mn4Si4Ni4 cuboctahedra, faces with four equivalent Ni(1)Mn8Si4 cuboctahedra, and faces with six equivalent Si(1)Mn8Ni4 cuboctahedra. Ni(1) is bonded to four equivalent Mn(1), four equivalent Mn(2), and four equivalent Si(1) atoms to form NiMn8Si4 cuboctahedra that share corners with four equivalent Ni(1)Mn8Si4 cuboctahedra, corners with eight equivalent Mn(1)Mn4Si4Ni4 cuboctahedra, edges with eight equivalent Mn(2)Mn4Si4Ni4 cuboctahedra, edges with eight equivalent Ni(1)Mn8Si4 cuboctahedra, edges with eight equivalent Si(1)Mn8Ni4 cuboctahedra, faces with four equivalent Mn(2)Mn4Si4Ni4 cuboctahedra, faces with four equivalent Ni(1)Mn8Si4 cuboctahedra, faces with four equivalent Si(1)Mn8Ni4 cuboctahedra, and faces with six equivalent Mn(1)Mn4Si4Ni4 cuboctahedra. Si(1) is bonded to four equivalent Mn(1), four equivalent Mn(2), and four equivalent Ni(1) atoms to form SiMn8Ni4 cuboctahedra that share corners with four equivalent Si(1)Mn8Ni4 cuboctahedra, corners with eight equivalent Mn(2)Mn4Si4Ni4 cuboctahedra, edges with eight equivalent Mn(1)Mn4Si4Ni4 cuboctahedra, edges with eight equivalent Ni(1)Mn8Si4 cuboctahedra, edges with eight equivalent Si(1)Mn8Ni4 cuboctahedra, faces with four equivalent Mn(1)Mn4Si4Ni4 cuboctahedra, faces with four equivalent Ni(1)Mn8Si4 cuboctahedra, faces with four equivalent Si(1)Mn8Ni4 cuboctahedra, and faces with six equivalent Mn(2)Mn4Si4Ni4 cuboctahedra.
Mn2NiSi crystallizes in the tetragonal I-4m2 space group. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to four equivalent Mn(2), four equivalent Ni(1), and four equivalent Si(1) atoms to form MnMn4Si4Ni4 cuboctahedra that share corners with four equivalent Mn(1)Mn4Si4Ni4 cuboctahedra, corners with eight equivalent Ni(1)Mn8Si4 cuboctahedra, edges with eight equivalent Mn(1)Mn4Si4Ni4 cuboctahedra, edges with eight equivalent Mn(2)Mn4Si4Ni4 cuboctahedra, edges with eight equivalent Si(1)Mn8Ni4 cuboctahedra, faces with four equivalent Mn(1)Mn4Si4Ni4 cuboctahedra, faces with four equivalent Mn(2)Mn4Si4Ni4 cuboctahedra, faces with four equivalent Si(1)Mn8Ni4 cuboctahedra, and faces with six equivalent Ni(1)Mn8Si4 cuboctahedra. All Mn(1)-Mn(2) bond lengths are 2.51 Å. All Mn(1)-Ni(1) bond lengths are 2.56 Å. All Mn(1)-Si(1) bond lengths are 2.51 Å. In the second Mn site, Mn(2) is bonded to four equivalent Mn(1), four equivalent Ni(1), and four equivalent Si(1) atoms to form MnMn4Si4Ni4 cuboctahedra that share corners with four equivalent Mn(2)Mn4Si4Ni4 cuboctahedra, corners with eight equivalent Si(1)Mn8Ni4 cuboctahedra, edges with eight equivalent Mn(1)Mn4Si4Ni4 cuboctahedra, edges with eight equivalent Mn(2)Mn4Si4Ni4 cuboctahedra, edges with eight equivalent Ni(1)Mn8Si4 cuboctahedra, faces with four equivalent Mn(1)Mn4Si4Ni4 cuboctahedra, faces with four equivalent Mn(2)Mn4Si4Ni4 cuboctahedra, faces with four equivalent Ni(1)Mn8Si4 cuboctahedra, and faces with six equivalent Si(1)Mn8Ni4 cuboctahedra. All Mn(2)-Ni(1) bond lengths are 2.51 Å. All Mn(2)-Si(1) bond lengths are 2.56 Å. Ni(1) is bonded to four equivalent Mn(1), four equivalent Mn(2), and four equivalent Si(1) atoms to form NiMn8Si4 cuboctahedra that share corners with four equivalent Ni(1)Mn8Si4 cuboctahedra, corners with eight equivalent Mn(1)Mn4Si4Ni4 cuboctahedra, edges with eight equivalent Mn(2)Mn4Si4Ni4 cuboctahedra, edges with eight equivalent Ni(1)Mn8Si4 cuboctahedra, edges with eight equivalent Si(1)Mn8Ni4 cuboctahedra, faces with four equivalent Mn(2)Mn4Si4Ni4 cuboctahedra, faces with four equivalent Ni(1)Mn8Si4 cuboctahedra, faces with four equivalent Si(1)Mn8Ni4 cuboctahedra, and faces with six equivalent Mn(1)Mn4Si4Ni4 cuboctahedra. All Ni(1)-Si(1) bond lengths are 2.51 Å. Si(1) is bonded to four equivalent Mn(1), four equivalent Mn(2), and four equivalent Ni(1) atoms to form SiMn8Ni4 cuboctahedra that share corners with four equivalent Si(1)Mn8Ni4 cuboctahedra, corners with eight equivalent Mn(2)Mn4Si4Ni4 cuboctahedra, edges with eight equivalent Mn(1)Mn4Si4Ni4 cuboctahedra, edges with eight equivalent Ni(1)Mn8Si4 cuboctahedra, edges with eight equivalent Si(1)Mn8Ni4 cuboctahedra, faces with four equivalent Mn(1)Mn4Si4Ni4 cuboctahedra, faces with four equivalent Ni(1)Mn8Si4 cuboctahedra, faces with four equivalent Si(1)Mn8Ni4 cuboctahedra, and faces with six equivalent Mn(2)Mn4Si4Ni4 cuboctahedra.