Ca5Hf2N6 crystallizes in the monoclinic C2/c space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent N(1) and two equivalent N(3) atoms to form distorted CaN4 trigonal pyramids that share corners with four equivalent Hf(1)N4 tetrahedra. In the second Ca site, Ca(2) is bonded in a distorted see-saw-like geometry to one N(1), one N(3), and two equivalent N(2) atoms. In the third Ca site, Ca(3) is bonded in a 5-coordinate geometry to one N(2), two equivalent N(1), and two equivalent N(3) atoms. Hf(1) is bonded to one N(1), one N(3), and two equivalent N(2) atoms to form HfN4 tetrahedra that share corners with two equivalent Ca(1)N4 trigonal pyramids and  an edgeedge with one Hf(1)N4 tetrahedra. There are three inequivalent N sites. In the first N site, N(2) is bonded in a 5-coordinate geometry to one Ca(3), two equivalent Ca(2), and two equivalent Hf(1) atoms. In the second N site, N(3) is bonded to one Ca(1), one Ca(2), two equivalent Ca(3), and one Hf(1) atom to form a mixture of distorted edge, face, and corner-sharing NCa4Hf square pyramids. In the third N site, N(1) is bonded to one Ca(1), one Ca(2), two equivalent Ca(3), and one Hf(1) atom to form a mixture of distorted edge and corner-sharing NCa4Hf trigonal bipyramids.
Ca5Hf2N6 crystallizes in the monoclinic C2/c space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent N(1) and two equivalent N(3) atoms to form distorted CaN4 trigonal pyramids that share corners with four equivalent Hf(1)N4 tetrahedra. Both Ca(1)-N(1) bond lengths are 2.41 Å. Both Ca(1)-N(3) bond lengths are 2.41 Å. In the second Ca site, Ca(2) is bonded in a distorted see-saw-like geometry to one N(1), one N(3), and two equivalent N(2) atoms. The Ca(2)-N(1) bond length is 2.78 Å. The Ca(2)-N(3) bond length is 2.37 Å. There is one shorter (2.37 Å) and one longer (2.53 Å) Ca(2)-N(2) bond length. In the third Ca site, Ca(3) is bonded in a 5-coordinate geometry to one N(2), two equivalent N(1), and two equivalent N(3) atoms. The Ca(3)-N(2) bond length is 2.88 Å. There is one shorter (2.47 Å) and one longer (2.49 Å) Ca(3)-N(1) bond length. There is one shorter (2.42 Å) and one longer (2.66 Å) Ca(3)-N(3) bond length. Hf(1) is bonded to one N(1), one N(3), and two equivalent N(2) atoms to form HfN4 tetrahedra that share corners with two equivalent Ca(1)N4 trigonal pyramids and  an edgeedge with one Hf(1)N4 tetrahedra. The Hf(1)-N(1) bond length is 2.04 Å. The Hf(1)-N(3) bond length is 2.03 Å. Both Hf(1)-N(2) bond lengths are 2.11 Å. There are three inequivalent N sites. In the first N site, N(2) is bonded in a 5-coordinate geometry to one Ca(3), two equivalent Ca(2), and two equivalent Hf(1) atoms. In the second N site, N(3) is bonded to one Ca(1), one Ca(2), two equivalent Ca(3), and one Hf(1) atom to form a mixture of distorted edge, face, and corner-sharing NCa4Hf square pyramids. In the third N site, N(1) is bonded to one Ca(1), one Ca(2), two equivalent Ca(3), and one Hf(1) atom to form a mixture of distorted edge and corner-sharing NCa4Hf trigonal bipyramids.