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HfB2 is hexagonal omega structure structured and crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Hf is bonded to twelve equivalent B atoms to form a mixture of edge and face-sharing HfB12 cuboctahedra. All Hf–B bond lengths are 2.52 Å. B is bonded in a 9-coordinate geometry to six equivalent Hf and three equivalent B atoms. All B–B bond lengths are 1.82 Å.
ZrB2(HfB2) is hexagonal omega structure-derived structured and crystallizes in the orthorhombic Pmmm space group. The structure is three-dimensional. Hf4+ is bonded to twelve B+1.50- atoms to form HfB12 cuboctahedra that share edges with four equivalent HfB12 cuboctahedra, edges with eight equivalent ZrB12 cuboctahedra, faces with four equivalent HfB12 cuboctahedra, and faces with four equivalent ZrB12 cuboctahedra. All Hf–B bond lengths are 2.53 Å. Zr2+ is bonded to twelve B+1.50- atoms to form ZrB12 cuboctahedra that share edges with four equivalent ZrB12 cuboctahedra, edges with eight equivalent HfB12 cuboctahedra, faces with four equivalent HfB12 cuboctahedra, and faces with four equivalent ZrB12 cuboctahedra. All Zr–B bond lengths are 2.54 Å. There are two inequivalent B+1.50- sites. In the first B+1.50- site, B+1.50- is bonded in a 9-coordinate geometry to two equivalent Hf4+, four equivalent Zr2+, and three B+1.50- atoms. There is two shorter (1.83 Å) and one longer (1.84 Å) B–B bond length. In the second B+1.50- site, B+1.50- is bonded in a 9-coordinate geometry to four equivalent Hf4+, two equivalent Zr2+, and three B+1.50- atoms. The B–B bond length is 1.81 Å.
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