Sr4Ru2O9 crystallizes in the trigonal P321 space group. There are three inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 10-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(5), and four equivalent O(3) atoms. In the second Sr site, Sr(2) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), and four equivalent O(4) atoms. In the third Sr site, Sr(3) is bonded in a 9-coordinate geometry to one O(5), two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. There are three inequivalent Ru sites. In the first Ru site, Ru(1) is bonded to three equivalent O(1) and three equivalent O(5) atoms to form face-sharing RuO6 octahedra. In the second Ru site, Ru(2) is bonded to three equivalent O(2) and three equivalent O(3) atoms to form face-sharing RuO6 octahedra. In the third Ru site, Ru(3) is bonded to three equivalent O(2) and three equivalent O(4) atoms to form face-sharing RuO6 octahedra. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Sr(1), one Sr(2), two equivalent Sr(3), and one Ru(1) atom to form distorted OSr4Ru square pyramids that share  a cornercorner with one O(5)Sr4Ru2 octahedra, corners with five equivalent O(2)Sr4Ru2 octahedra, corners with two equivalent O(1)Sr4Ru square pyramids, edges with two equivalent O(1)Sr4Ru square pyramids,  a faceface with one O(2)Sr4Ru2 octahedra, and faces with two equivalent O(5)Sr4Ru2 octahedra. The corner-sharing octahedral tilt angles range from 8-57°. In the second O site, O(2) is bonded to one Sr(1), one Sr(2), two equivalent Sr(3), one Ru(2), and one Ru(3) atom to form distorted OSr4Ru2 octahedra that share corners with two equivalent O(2)Sr4Ru2 octahedra, corners with two equivalent O(5)Sr4Ru2 octahedra, corners with five equivalent O(1)Sr4Ru square pyramids,  an edgeedge with one O(5)Sr4Ru2 octahedra, faces with two equivalent O(2)Sr4Ru2 octahedra, and  a faceface with one O(1)Sr4Ru square pyramid. The corner-sharing octahedral tilt angles range from 38-55°. In the third O site, O(3) is bonded in a 5-coordinate geometry to two equivalent Sr(1), two equivalent Sr(3), and one Ru(2) atom. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to two equivalent Sr(2), two equivalent Sr(3), and one Ru(3) atom. In the fifth O site, O(5) is bonded to two equivalent Sr(1), two equivalent Sr(3), and two equivalent Ru(1) atoms to form distorted OSr4Ru2 octahedra that share corners with four equivalent O(2)Sr4Ru2 octahedra, corners with two equivalent O(1)Sr4Ru square pyramids, edges with two equivalent O(2)Sr4Ru2 octahedra, faces with two equivalent O(5)Sr4Ru2 octahedra, and faces with four equivalent O(1)Sr4Ru square pyramids. The corner-sharing octahedral tilt angles range from 54-55°.
Sr4Ru2O9 crystallizes in the trigonal P321 space group. There are three inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 10-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(5), and four equivalent O(3) atoms. Both Sr(1)-O(1) bond lengths are 2.70 Å. Both Sr(1)-O(2) bond lengths are 2.56 Å. Both Sr(1)-O(5) bond lengths are 2.75 Å. There are two shorter (2.68 Å) and two longer (2.98 Å) Sr(1)-O(3) bond lengths. In the second Sr site, Sr(2) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), and four equivalent O(4) atoms. Both Sr(2)-O(1) bond lengths are 2.49 Å. Both Sr(2)-O(2) bond lengths are 2.54 Å. There are two shorter (2.62 Å) and two longer (2.88 Å) Sr(2)-O(4) bond lengths. In the third Sr site, Sr(3) is bonded in a 9-coordinate geometry to one O(5), two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. The Sr(3)-O(5) bond length is 2.54 Å. There is one shorter (2.72 Å) and one longer (2.78 Å) Sr(3)-O(1) bond length. There is one shorter (2.61 Å) and one longer (2.87 Å) Sr(3)-O(2) bond length. There is one shorter (2.48 Å) and one longer (2.75 Å) Sr(3)-O(3) bond length. There is one shorter (2.53 Å) and one longer (2.69 Å) Sr(3)-O(4) bond length. There are three inequivalent Ru sites. In the first Ru site, Ru(1) is bonded to three equivalent O(1) and three equivalent O(5) atoms to form face-sharing RuO6 octahedra. All Ru(1)-O(1) bond lengths are 1.90 Å. All Ru(1)-O(5) bond lengths are 2.03 Å. In the second Ru site, Ru(2) is bonded to three equivalent O(2) and three equivalent O(3) atoms to form face-sharing RuO6 octahedra. All Ru(2)-O(2) bond lengths are 2.09 Å. All Ru(2)-O(3) bond lengths are 1.86 Å. In the third Ru site, Ru(3) is bonded to three equivalent O(2) and three equivalent O(4) atoms to form face-sharing RuO6 octahedra. All Ru(3)-O(2) bond lengths are 2.07 Å. All Ru(3)-O(4) bond lengths are 1.90 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Sr(1), one Sr(2), two equivalent Sr(3), and one Ru(1) atom to form distorted OSr4Ru square pyramids that share  a cornercorner with one O(5)Sr4Ru2 octahedra, corners with five equivalent O(2)Sr4Ru2 octahedra, corners with two equivalent O(1)Sr4Ru square pyramids, edges with two equivalent O(1)Sr4Ru square pyramids,  a faceface with one O(2)Sr4Ru2 octahedra, and faces with two equivalent O(5)Sr4Ru2 octahedra. The corner-sharing octahedral tilt angles range from 8-57°. In the second O site, O(2) is bonded to one Sr(1), one Sr(2), two equivalent Sr(3), one Ru(2), and one Ru(3) atom to form distorted OSr4Ru2 octahedra that share corners with two equivalent O(2)Sr4Ru2 octahedra, corners with two equivalent O(5)Sr4Ru2 octahedra, corners with five equivalent O(1)Sr4Ru square pyramids,  an edgeedge with one O(5)Sr4Ru2 octahedra, faces with two equivalent O(2)Sr4Ru2 octahedra, and  a faceface with one O(1)Sr4Ru square pyramid. The corner-sharing octahedral tilt angles range from 38-55°. In the third O site, O(3) is bonded in a 5-coordinate geometry to two equivalent Sr(1), two equivalent Sr(3), and one Ru(2) atom. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to two equivalent Sr(2), two equivalent Sr(3), and one Ru(3) atom. In the fifth O site, O(5) is bonded to two equivalent Sr(1), two equivalent Sr(3), and two equivalent Ru(1) atoms to form distorted OSr4Ru2 octahedra that share corners with four equivalent O(2)Sr4Ru2 octahedra, corners with two equivalent O(1)Sr4Ru square pyramids, edges with two equivalent O(2)Sr4Ru2 octahedra, faces with two equivalent O(5)Sr4Ru2 octahedra, and faces with four equivalent O(1)Sr4Ru square pyramids. The corner-sharing octahedral tilt angles range from 54-55°.