Fe3Ni is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to eight equivalent Fe(2) and four equivalent Ni(1) atoms to form FeFe8Ni4 cuboctahedra that share corners with four equivalent Fe(1)Fe8Ni4 cuboctahedra, corners with eight equivalent Ni(1)Fe12 cuboctahedra, edges with eight equivalent Fe(1)Fe8Ni4 cuboctahedra, edges with sixteen equivalent Fe(2)Fe8Ni4 cuboctahedra, faces with four equivalent Fe(1)Fe8Ni4 cuboctahedra, faces with six equivalent Ni(1)Fe12 cuboctahedra, and faces with eight equivalent Fe(2)Fe8Ni4 cuboctahedra. In the second Fe site, Fe(2) is bonded to four equivalent Fe(1), four equivalent Fe(2), and four equivalent Ni(1) atoms to form FeFe8Ni4 cuboctahedra that share corners with twelve equivalent Fe(2)Fe8Ni4 cuboctahedra, edges with eight equivalent Fe(1)Fe8Ni4 cuboctahedra, edges with eight equivalent Fe(2)Fe8Ni4 cuboctahedra, edges with eight equivalent Ni(1)Fe12 cuboctahedra, faces with four equivalent Fe(1)Fe8Ni4 cuboctahedra, faces with four equivalent Ni(1)Fe12 cuboctahedra, and faces with ten equivalent Fe(2)Fe8Ni4 cuboctahedra. Ni(1) is bonded to four equivalent Fe(1) and eight equivalent Fe(2) atoms to form NiFe12 cuboctahedra that share corners with four equivalent Ni(1)Fe12 cuboctahedra, corners with eight equivalent Fe(1)Fe8Ni4 cuboctahedra, edges with eight equivalent Ni(1)Fe12 cuboctahedra, edges with sixteen equivalent Fe(2)Fe8Ni4 cuboctahedra, faces with four equivalent Ni(1)Fe12 cuboctahedra, faces with six equivalent Fe(1)Fe8Ni4 cuboctahedra, and faces with eight equivalent Fe(2)Fe8Ni4 cuboctahedra.
Fe3Ni is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to eight equivalent Fe(2) and four equivalent Ni(1) atoms to form FeFe8Ni4 cuboctahedra that share corners with four equivalent Fe(1)Fe8Ni4 cuboctahedra, corners with eight equivalent Ni(1)Fe12 cuboctahedra, edges with eight equivalent Fe(1)Fe8Ni4 cuboctahedra, edges with sixteen equivalent Fe(2)Fe8Ni4 cuboctahedra, faces with four equivalent Fe(1)Fe8Ni4 cuboctahedra, faces with six equivalent Ni(1)Fe12 cuboctahedra, and faces with eight equivalent Fe(2)Fe8Ni4 cuboctahedra. All Fe(1)-Fe(2) bond lengths are 2.57 Å. All Fe(1)-Ni(1) bond lengths are 2.49 Å. In the second Fe site, Fe(2) is bonded to four equivalent Fe(1), four equivalent Fe(2), and four equivalent Ni(1) atoms to form FeFe8Ni4 cuboctahedra that share corners with twelve equivalent Fe(2)Fe8Ni4 cuboctahedra, edges with eight equivalent Fe(1)Fe8Ni4 cuboctahedra, edges with eight equivalent Fe(2)Fe8Ni4 cuboctahedra, edges with eight equivalent Ni(1)Fe12 cuboctahedra, faces with four equivalent Fe(1)Fe8Ni4 cuboctahedra, faces with four equivalent Ni(1)Fe12 cuboctahedra, and faces with ten equivalent Fe(2)Fe8Ni4 cuboctahedra. All Fe(2)-Fe(2) bond lengths are 2.49 Å. All Fe(2)-Ni(1) bond lengths are 2.57 Å. Ni(1) is bonded to four equivalent Fe(1) and eight equivalent Fe(2) atoms to form NiFe12 cuboctahedra that share corners with four equivalent Ni(1)Fe12 cuboctahedra, corners with eight equivalent Fe(1)Fe8Ni4 cuboctahedra, edges with eight equivalent Ni(1)Fe12 cuboctahedra, edges with sixteen equivalent Fe(2)Fe8Ni4 cuboctahedra, faces with four equivalent Ni(1)Fe12 cuboctahedra, faces with six equivalent Fe(1)Fe8Ni4 cuboctahedra, and faces with eight equivalent Fe(2)Fe8Ni4 cuboctahedra.