Nb4AlN3 is MAX Phase-like structured and crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to three equivalent N(1) and three equivalent N(2) atoms to form a mixture of distorted corner and edge-sharing NbN6 pentagonal pyramids. In the second Nb site, Nb(2) is bonded in a 3-coordinate geometry to three equivalent Al(1) and three equivalent N(2) atoms. Al(1) is bonded to six equivalent Nb(2) and six equivalent Al(1) atoms to form AlNb6Al6 cuboctahedra that share corners with six equivalent Al(1)Nb6Al6 cuboctahedra, corners with six equivalent N(2)Nb6 octahedra, edges with six equivalent Al(1)Nb6Al6 cuboctahedra, edges with six equivalent N(2)Nb6 octahedra, and faces with six equivalent Al(1)Nb6Al6 cuboctahedra. The corner-sharing octahedral tilt angles are 13°. There are two inequivalent N sites. In the first N site, N(1) is bonded to six equivalent Nb(1) atoms to form a mixture of face, corner, and edge-sharing NNb6 octahedra. The corner-sharing octahedral tilt angles are 46°. In the second N site, N(2) is bonded to three equivalent Nb(1) and three equivalent Nb(2) atoms to form NNb6 octahedra that share corners with three equivalent Al(1)Nb6Al6 cuboctahedra, corners with six equivalent N(1)Nb6 octahedra, edges with three equivalent Al(1)Nb6Al6 cuboctahedra, edges with six equivalent N(2)Nb6 octahedra, and  a faceface with one N(1)Nb6 octahedra. The corner-sharing octahedral tilt angles are 46°.
Nb4AlN3 is MAX Phase-like structured and crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to three equivalent N(1) and three equivalent N(2) atoms to form a mixture of distorted corner and edge-sharing NbN6 pentagonal pyramids. All Nb(1)-N(1) bond lengths are 2.24 Å. All Nb(1)-N(2) bond lengths are 2.21 Å. In the second Nb site, Nb(2) is bonded in a 3-coordinate geometry to three equivalent Al(1) and three equivalent N(2) atoms. All Nb(2)-Al(1) bond lengths are 2.83 Å. All Nb(2)-N(2) bond lengths are 2.23 Å. Al(1) is bonded to six equivalent Nb(2) and six equivalent Al(1) atoms to form AlNb6Al6 cuboctahedra that share corners with six equivalent Al(1)Nb6Al6 cuboctahedra, corners with six equivalent N(2)Nb6 octahedra, edges with six equivalent Al(1)Nb6Al6 cuboctahedra, edges with six equivalent N(2)Nb6 octahedra, and faces with six equivalent Al(1)Nb6Al6 cuboctahedra. The corner-sharing octahedral tilt angles are 13°. All Al(1)-Al(1) bond lengths are 3.01 Å. There are two inequivalent N sites. In the first N site, N(1) is bonded to six equivalent Nb(1) atoms to form a mixture of face, corner, and edge-sharing NNb6 octahedra. The corner-sharing octahedral tilt angles are 46°. In the second N site, N(2) is bonded to three equivalent Nb(1) and three equivalent Nb(2) atoms to form NNb6 octahedra that share corners with three equivalent Al(1)Nb6Al6 cuboctahedra, corners with six equivalent N(1)Nb6 octahedra, edges with three equivalent Al(1)Nb6Al6 cuboctahedra, edges with six equivalent N(2)Nb6 octahedra, and  a faceface with one N(1)Nb6 octahedra. The corner-sharing octahedral tilt angles are 46°.