Sr2Hf7O16 crystallizes in the trigonal R-3 space group. There are six inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a distorted body-centered cubic geometry to one O(1), one O(4), and six equivalent O(2) atoms. In the second Sr site, Sr(1) is bonded in a distorted body-centered cubic geometry to one O(1), one O(4), and six equivalent O(2) atoms. In the third Sr site, Sr(1) is bonded in a distorted body-centered cubic geometry to one O(1), one O(4), and six equivalent O(2) atoms. In the fourth Sr site, Sr(1) is bonded in a distorted body-centered cubic geometry to one O(1), one O(4), and six equivalent O(2) atoms. In the fifth Sr site, Sr(1) is bonded in a distorted body-centered cubic geometry to one O(1), one O(4), and six equivalent O(2) atoms. In the sixth Sr site, Sr(1) is bonded in a distorted body-centered cubic geometry to one O(1), one O(4), and six equivalent O(2) atoms. There are nine inequivalent Hf sites. In the first Hf site, Hf(1) is bonded to six equivalent O(2) atoms to form corner-sharing HfO6 octahedra. In the second Hf site, Hf(2) is bonded to one O(1), one O(2), one O(4), and four equivalent O(3) atoms to form distorted HfO7 pentagonal bipyramids that share  a cornercorner with one Hf(1)O6 octahedra; corners with two equivalent Hf(2)O7 pentagonal bipyramids; and edges with seven Hf(2,2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 40°. In the third Hf site, Hf(2) is bonded to one O(1), one O(2), one O(4), and four equivalent O(3) atoms to form distorted HfO7 pentagonal bipyramids that share  a cornercorner with one Hf(1)O6 octahedra; corners with two equivalent Hf(2)O7 pentagonal bipyramids; and edges with seven Hf(2,2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 40°. In the fourth Hf site, Hf(1) is bonded to six equivalent O(2) atoms to form corner-sharing HfO6 octahedra. In the fifth Hf site, Hf(2) is bonded to one O(1), one O(2), one O(4), and four equivalent O(3) atoms to form distorted HfO7 pentagonal bipyramids that share  a cornercorner with one Hf(1)O6 octahedra; corners with two equivalent Hf(2)O7 pentagonal bipyramids; and edges with seven Hf(2,2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 40°. In the sixth Hf site, Hf(2) is bonded to one O(1), one O(2), one O(4), and four equivalent O(3) atoms to form distorted HfO7 pentagonal bipyramids that share  a cornercorner with one Hf(1)O6 octahedra; corners with two equivalent Hf(2)O7 pentagonal bipyramids; and edges with seven Hf(2,2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 40°. In the seventh Hf site, Hf(1) is bonded to six equivalent O(2) atoms to form corner-sharing HfO6 octahedra. In the eighth Hf site, Hf(2) is bonded to one O(1), one O(2), one O(4), and four equivalent O(3) atoms to form distorted HfO7 pentagonal bipyramids that share  a cornercorner with one Hf(1)O6 octahedra; corners with two equivalent Hf(2)O7 pentagonal bipyramids; and edges with seven Hf(2,2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 40°. In the ninth Hf site, Hf(2) is bonded to one O(1), one O(2), one O(4), and four equivalent O(3) atoms to form distorted HfO7 pentagonal bipyramids that share  a cornercorner with one Hf(1)O6 octahedra; corners with two equivalent Hf(2)O7 pentagonal bipyramids; and edges with seven Hf(2,2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 40°. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Sr(1) and three equivalent Hf(2) atoms to form distorted OSrHf3 tetrahedra that share corners with four equivalent O(4)SrHf3 tetrahedra, corners with six equivalent O(3)Hf4 tetrahedra, corners with three equivalent O(2)Sr2Hf2 trigonal pyramids, edges with three equivalent O(3)Hf4 tetrahedra, and edges with three equivalent O(2)Sr2Hf2 trigonal pyramids. In the second O site, O(2) is bonded to two Sr(1,1); one Hf(1); and one Hf(2) atom to form distorted OSr2Hf2 trigonal pyramids that share  a cornercorner with one O(1)SrHf3 tetrahedra,  a cornercorner with one O(4)SrHf3 tetrahedra, corners with four equivalent O(3)Hf4 tetrahedra, corners with nine equivalent O(2)Sr2Hf2 trigonal pyramids,  an edgeedge with one O(1)SrHf3 tetrahedra,  an edgeedge with one O(4)SrHf3 tetrahedra, and edges with three equivalent O(2)Sr2Hf2 trigonal pyramids. In the third O site, O(3) is bonded to four Hf(2,2) atoms to form distorted OHf4 tetrahedra that share corners with two equivalent O(1)SrHf3 tetrahedra, corners with two equivalent O(4)SrHf3 tetrahedra, corners with six equivalent O(3)Hf4 tetrahedra, corners with four equivalent O(2)Sr2Hf2 trigonal pyramids,  an edgeedge with one O(1)SrHf3 tetrahedra,  an edgeedge with one O(4)SrHf3 tetrahedra, and edges with three equivalent O(3)Hf4 tetrahedra. In the fourth O site, O(4) is bonded to one Sr(1) and three equivalent Hf(2) atoms to form OSrHf3 tetrahedra that share corners with four equivalent O(1)SrHf3 tetrahedra, corners with six equivalent O(3)Hf4 tetrahedra, corners with three equivalent O(2)Sr2Hf2 trigonal pyramids, edges with three equivalent O(3)Hf4 tetrahedra, and edges with three equivalent O(2)Sr2Hf2 trigonal pyramids.
Sr2Hf7O16 crystallizes in the trigonal R-3 space group. There are six inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a distorted body-centered cubic geometry to one O(1), one O(4), and six equivalent O(2) atoms. The Sr(1)-O(1) bond length is 2.60 Å. The Sr(1)-O(4) bond length is 2.56 Å. There are three shorter (2.57 Å) and three longer (2.61 Å) Sr(1)-O(2) bond lengths. In the second Sr site, Sr(1) is bonded in a distorted body-centered cubic geometry to one O(1), one O(4), and six equivalent O(2) atoms. The Sr(1)-O(1) bond length is 2.60 Å. The Sr(1)-O(4) bond length is 2.56 Å. There are three shorter (2.57 Å) and three longer (2.61 Å) Sr(1)-O(2) bond lengths. In the third Sr site, Sr(1) is bonded in a distorted body-centered cubic geometry to one O(1), one O(4), and six equivalent O(2) atoms. The Sr(1)-O(1) bond length is 2.60 Å. The Sr(1)-O(4) bond length is 2.56 Å. There are three shorter (2.57 Å) and three longer (2.61 Å) Sr(1)-O(2) bond lengths. In the fourth Sr site, Sr(1) is bonded in a distorted body-centered cubic geometry to one O(1), one O(4), and six equivalent O(2) atoms. The Sr(1)-O(1) bond length is 2.60 Å. The Sr(1)-O(4) bond length is 2.56 Å. There are three shorter (2.57 Å) and three longer (2.61 Å) Sr(1)-O(2) bond lengths. In the fifth Sr site, Sr(1) is bonded in a distorted body-centered cubic geometry to one O(1), one O(4), and six equivalent O(2) atoms. The Sr(1)-O(1) bond length is 2.60 Å. The Sr(1)-O(4) bond length is 2.56 Å. There are three shorter (2.57 Å) and three longer (2.61 Å) Sr(1)-O(2) bond lengths. In the sixth Sr site, Sr(1) is bonded in a distorted body-centered cubic geometry to one O(1), one O(4), and six equivalent O(2) atoms. The Sr(1)-O(1) bond length is 2.60 Å. The Sr(1)-O(4) bond length is 2.56 Å. There are three shorter (2.57 Å) and three longer (2.61 Å) Sr(1)-O(2) bond lengths. There are nine inequivalent Hf sites. In the first Hf site, Hf(1) is bonded to six equivalent O(2) atoms to form corner-sharing HfO6 octahedra. All Hf(1)-O(2) bond lengths are 2.08 Å. In the second Hf site, Hf(2) is bonded to one O(1), one O(2), one O(4), and four equivalent O(3) atoms to form distorted HfO7 pentagonal bipyramids that share  a cornercorner with one Hf(1)O6 octahedra; corners with two equivalent Hf(2)O7 pentagonal bipyramids; and edges with seven Hf(2,2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 40°. The Hf(2)-O(1) bond length is 2.06 Å. The Hf(2)-O(2) bond length is 2.02 Å. The Hf(2)-O(4) bond length is 2.09 Å. There are a spread of Hf(2)-O(3) bond distances ranging from 2.13-2.30 Å. In the third Hf site, Hf(2) is bonded to one O(1), one O(2), one O(4), and four equivalent O(3) atoms to form distorted HfO7 pentagonal bipyramids that share  a cornercorner with one Hf(1)O6 octahedra; corners with two equivalent Hf(2)O7 pentagonal bipyramids; and edges with seven Hf(2,2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 40°. The Hf(2)-O(1) bond length is 2.06 Å. The Hf(2)-O(2) bond length is 2.02 Å. The Hf(2)-O(4) bond length is 2.09 Å. There are a spread of Hf(2)-O(3) bond distances ranging from 2.13-2.30 Å. In the fourth Hf site, Hf(1) is bonded to six equivalent O(2) atoms to form corner-sharing HfO6 octahedra. All Hf(1)-O(2) bond lengths are 2.08 Å. In the fifth Hf site, Hf(2) is bonded to one O(1), one O(2), one O(4), and four equivalent O(3) atoms to form distorted HfO7 pentagonal bipyramids that share  a cornercorner with one Hf(1)O6 octahedra; corners with two equivalent Hf(2)O7 pentagonal bipyramids; and edges with seven Hf(2,2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 40°. The Hf(2)-O(1) bond length is 2.06 Å. The Hf(2)-O(2) bond length is 2.02 Å. The Hf(2)-O(4) bond length is 2.09 Å. There are a spread of Hf(2)-O(3) bond distances ranging from 2.13-2.30 Å. In the sixth Hf site, Hf(2) is bonded to one O(1), one O(2), one O(4), and four equivalent O(3) atoms to form distorted HfO7 pentagonal bipyramids that share  a cornercorner with one Hf(1)O6 octahedra; corners with two equivalent Hf(2)O7 pentagonal bipyramids; and edges with seven Hf(2,2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 40°. The Hf(2)-O(1) bond length is 2.06 Å. The Hf(2)-O(2) bond length is 2.02 Å. The Hf(2)-O(4) bond length is 2.09 Å. There are a spread of Hf(2)-O(3) bond distances ranging from 2.13-2.30 Å. In the seventh Hf site, Hf(1) is bonded to six equivalent O(2) atoms to form corner-sharing HfO6 octahedra. All Hf(1)-O(2) bond lengths are 2.08 Å. In the eighth Hf site, Hf(2) is bonded to one O(1), one O(2), one O(4), and four equivalent O(3) atoms to form distorted HfO7 pentagonal bipyramids that share  a cornercorner with one Hf(1)O6 octahedra; corners with two equivalent Hf(2)O7 pentagonal bipyramids; and edges with seven Hf(2,2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 40°. The Hf(2)-O(1) bond length is 2.06 Å. The Hf(2)-O(2) bond length is 2.02 Å. The Hf(2)-O(4) bond length is 2.09 Å. There are a spread of Hf(2)-O(3) bond distances ranging from 2.13-2.30 Å. In the ninth Hf site, Hf(2) is bonded to one O(1), one O(2), one O(4), and four equivalent O(3) atoms to form distorted HfO7 pentagonal bipyramids that share  a cornercorner with one Hf(1)O6 octahedra; corners with two equivalent Hf(2)O7 pentagonal bipyramids; and edges with seven Hf(2,2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 40°. The Hf(2)-O(1) bond length is 2.06 Å. The Hf(2)-O(2) bond length is 2.02 Å. The Hf(2)-O(4) bond length is 2.09 Å. There are a spread of Hf(2)-O(3) bond distances ranging from 2.13-2.30 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Sr(1) and three equivalent Hf(2) atoms to form distorted OSrHf3 tetrahedra that share corners with four equivalent O(4)SrHf3 tetrahedra, corners with six equivalent O(3)Hf4 tetrahedra, corners with three equivalent O(2)Sr2Hf2 trigonal pyramids, edges with three equivalent O(3)Hf4 tetrahedra, and edges with three equivalent O(2)Sr2Hf2 trigonal pyramids. In the second O site, O(2) is bonded to two Sr(1,1); one Hf(1); and one Hf(2) atom to form distorted OSr2Hf2 trigonal pyramids that share  a cornercorner with one O(1)SrHf3 tetrahedra,  a cornercorner with one O(4)SrHf3 tetrahedra, corners with four equivalent O(3)Hf4 tetrahedra, corners with nine equivalent O(2)Sr2Hf2 trigonal pyramids,  an edgeedge with one O(1)SrHf3 tetrahedra,  an edgeedge with one O(4)SrHf3 tetrahedra, and edges with three equivalent O(2)Sr2Hf2 trigonal pyramids. In the third O site, O(3) is bonded to four Hf(2,2) atoms to form distorted OHf4 tetrahedra that share corners with two equivalent O(1)SrHf3 tetrahedra, corners with two equivalent O(4)SrHf3 tetrahedra, corners with six equivalent O(3)Hf4 tetrahedra, corners with four equivalent O(2)Sr2Hf2 trigonal pyramids,  an edgeedge with one O(1)SrHf3 tetrahedra,  an edgeedge with one O(4)SrHf3 tetrahedra, and edges with three equivalent O(3)Hf4 tetrahedra. In the fourth O site, O(4) is bonded to one Sr(1) and three equivalent Hf(2) atoms to form OSrHf3 tetrahedra that share corners with four equivalent O(1)SrHf3 tetrahedra, corners with six equivalent O(3)Hf4 tetrahedra, corners with three equivalent O(2)Sr2Hf2 trigonal pyramids, edges with three equivalent O(3)Hf4 tetrahedra, and edges with three equivalent O(2)Sr2Hf2 trigonal pyramids.