Sr3Hf2O7 crystallizes in the orthorhombic Ccce space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 9-coordinate geometry to four equivalent O(2) and five equivalent O(1) atoms. In the second Sr site, Sr(2) is bonded to four O(3,3) and eight equivalent O(2) atoms to form distorted SrO12 cuboctahedra that share corners with four equivalent Sr(2)O12 cuboctahedra, faces with four equivalent Sr(2)O12 cuboctahedra, and faces with eight equivalent Hf(1)O6 octahedra. Hf(1) is bonded to one O(1), one O(3), and four equivalent O(2) atoms to form HfO6 octahedra that share corners with five equivalent Hf(1)O6 octahedra and faces with four equivalent Sr(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-22°. There are five inequivalent O sites. In the first O site, O(3) is bonded to four equivalent Sr(2) and two equivalent Hf(1) atoms to form distorted OSr4Hf2 octahedra that share corners with two equivalent O(1)Sr5Hf octahedra, corners with four equivalent O(3)Sr4Hf2 octahedra, and edges with four equivalent O(3)Sr4Hf2 octahedra. The corner-sharing octahedra are not tilted. In the second O site, O(3) is bonded to four equivalent Sr(2) and two equivalent Hf(1) atoms to form distorted OSr4Hf2 octahedra that share corners with two equivalent O(1)Sr5Hf octahedra, corners with four equivalent O(3)Sr4Hf2 octahedra, and edges with four equivalent O(3)Sr4Hf2 octahedra. The corner-sharing octahedra are not tilted. In the third O site, O(1) is bonded to five equivalent Sr(1) and one Hf(1) atom to form distorted OSr5Hf octahedra that share  a cornercorner with one O(3)Sr4Hf2 octahedra, corners with four equivalent O(1)Sr5Hf octahedra, and edges with eight equivalent O(1)Sr5Hf octahedra. The corner-sharing octahedral tilt angles range from 0-6°. In the fourth O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Hf(1) atoms. In the fifth O site, O(3) is bonded to four equivalent Sr(2) and two equivalent Hf(1) atoms to form distorted OSr4Hf2 octahedra that share corners with two equivalent O(1)Sr5Hf octahedra, corners with four equivalent O(3)Sr4Hf2 octahedra, and edges with four equivalent O(3)Sr4Hf2 octahedra. The corner-sharing octahedra are not tilted.
Sr3Hf2O7 crystallizes in the orthorhombic Ccce space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 9-coordinate geometry to four equivalent O(2) and five equivalent O(1) atoms. There are two shorter (2.54 Å) and two longer (3.10 Å) Sr(1)-O(2) bond lengths. There is one shorter (2.46 Å) and four longer (2.86 Å) Sr(1)-O(1) bond lengths. In the second Sr site, Sr(2) is bonded to four O(3,3) and eight equivalent O(2) atoms to form distorted SrO12 cuboctahedra that share corners with four equivalent Sr(2)O12 cuboctahedra, faces with four equivalent Sr(2)O12 cuboctahedra, and faces with eight equivalent Hf(1)O6 octahedra. All Sr(2)-O(3,3) bond lengths are 2.86 Å. There are four shorter (2.62 Å) and four longer (3.17 Å) Sr(2)-O(2) bond lengths. Hf(1) is bonded to one O(1), one O(3), and four equivalent O(2) atoms to form HfO6 octahedra that share corners with five equivalent Hf(1)O6 octahedra and faces with four equivalent Sr(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-22°. The Hf(1)-O(1) bond length is 2.08 Å. The Hf(1)-O(3) bond length is 2.09 Å. All Hf(1)-O(2) bond lengths are 2.06 Å. There are five inequivalent O sites. In the first O site, O(3) is bonded to four equivalent Sr(2) and two equivalent Hf(1) atoms to form distorted OSr4Hf2 octahedra that share corners with two equivalent O(1)Sr5Hf octahedra, corners with four equivalent O(3)Sr4Hf2 octahedra, and edges with four equivalent O(3)Sr4Hf2 octahedra. The corner-sharing octahedra are not tilted. Both O(3)-Hf(1) bond lengths are 2.09 Å. In the second O site, O(3) is bonded to four equivalent Sr(2) and two equivalent Hf(1) atoms to form distorted OSr4Hf2 octahedra that share corners with two equivalent O(1)Sr5Hf octahedra, corners with four equivalent O(3)Sr4Hf2 octahedra, and edges with four equivalent O(3)Sr4Hf2 octahedra. The corner-sharing octahedra are not tilted. All O(3)-Sr(2) bond lengths are 2.86 Å. Both O(3)-Hf(1) bond lengths are 2.09 Å. In the third O site, O(1) is bonded to five equivalent Sr(1) and one Hf(1) atom to form distorted OSr5Hf octahedra that share  a cornercorner with one O(3)Sr4Hf2 octahedra, corners with four equivalent O(1)Sr5Hf octahedra, and edges with eight equivalent O(1)Sr5Hf octahedra. The corner-sharing octahedral tilt angles range from 0-6°. In the fourth O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Hf(1) atoms. In the fifth O site, O(3) is bonded to four equivalent Sr(2) and two equivalent Hf(1) atoms to form distorted OSr4Hf2 octahedra that share corners with two equivalent O(1)Sr5Hf octahedra, corners with four equivalent O(3)Sr4Hf2 octahedra, and edges with four equivalent O(3)Sr4Hf2 octahedra. The corner-sharing octahedra are not tilted.