Mg17Sr2 is Bergman Structure: Mg32(Al,Zn)49 Bergman-derived structured and crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 20-coordinate geometry to two equivalent Mg(2), six equivalent Mg(1), six equivalent Mg(3), and six equivalent Mg(4) atoms. In the second Sr site, Sr(2) is bonded in a 12-coordinate geometry to six equivalent Mg(1) and six equivalent Mg(4) atoms. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 11-coordinate geometry to one Sr(1), one Sr(2), one Mg(2), two equivalent Mg(1), two equivalent Mg(3), and four equivalent Mg(4) atoms. In the second Mg site, Mg(2) is bonded in a 14-coordinate geometry to one Sr(1), one Mg(2), three equivalent Mg(1), three equivalent Mg(3), and six equivalent Mg(4) atoms. In the third Mg site, Mg(3) is bonded to two equivalent Sr(1), two equivalent Mg(2), four equivalent Mg(1), and four equivalent Mg(4) atoms to form a mixture of distorted face and corner-sharing MgSr2Mg10 cuboctahedra. In the fourth Mg site, Mg(4) is bonded in a 12-coordinate geometry to one Sr(1), one Sr(2), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), and four equivalent Mg(1) atoms.
Mg17Sr2 is Bergman Structure: Mg32(Al,Zn)49 Bergman-derived structured and crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 20-coordinate geometry to two equivalent Mg(2), six equivalent Mg(1), six equivalent Mg(3), and six equivalent Mg(4) atoms. Both Sr(1)-Mg(2) bond lengths are 3.62 Å. All Sr(1)-Mg(1) bond lengths are 3.83 Å. All Sr(1)-Mg(3) bond lengths are 3.97 Å. All Sr(1)-Mg(4) bond lengths are 3.73 Å. In the second Sr site, Sr(2) is bonded in a 12-coordinate geometry to six equivalent Mg(1) and six equivalent Mg(4) atoms. All Sr(2)-Mg(1) bond lengths are 3.82 Å. All Sr(2)-Mg(4) bond lengths are 3.66 Å. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 11-coordinate geometry to one Sr(1), one Sr(2), one Mg(2), two equivalent Mg(1), two equivalent Mg(3), and four equivalent Mg(4) atoms. The Mg(1)-Mg(2) bond length is 3.29 Å. Both Mg(1)-Mg(1) bond lengths are 3.05 Å. Both Mg(1)-Mg(3) bond lengths are 3.03 Å. There are two shorter (3.17 Å) and two longer (3.19 Å) Mg(1)-Mg(4) bond lengths. In the second Mg site, Mg(2) is bonded in a 14-coordinate geometry to one Sr(1), one Mg(2), three equivalent Mg(1), three equivalent Mg(3), and six equivalent Mg(4) atoms. The Mg(2)-Mg(2) bond length is 3.03 Å. All Mg(2)-Mg(3) bond lengths are 3.20 Å. All Mg(2)-Mg(4) bond lengths are 3.46 Å. In the third Mg site, Mg(3) is bonded to two equivalent Sr(1), two equivalent Mg(2), four equivalent Mg(1), and four equivalent Mg(4) atoms to form a mixture of distorted face and corner-sharing MgSr2Mg10 cuboctahedra. All Mg(3)-Mg(4) bond lengths are 3.04 Å. In the fourth Mg site, Mg(4) is bonded in a 12-coordinate geometry to one Sr(1), one Sr(2), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), and four equivalent Mg(1) atoms. There is one shorter (3.03 Å) and one longer (3.18 Å) Mg(4)-Mg(4) bond length.