Sr8MgP4(O4I)4 crystallizes in the triclinic P1 space group. There are eight inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 5-coordinate geometry to one O(1), one O(10), one O(13), one O(15), one O(5), one I(3), and one I(4) atom. In the second Sr site, Sr(2) is bonded in a 7-coordinate geometry to one Mg(1), one O(16), one O(2), one O(7), one I(1), one I(3), and one I(4) atom. In the third Sr site, Sr(3) is bonded in a 8-coordinate geometry to one O(12), one O(13), one O(15), one O(2), one O(3), one O(6), one O(7), and one I(1) atom. In the fourth Sr site, Sr(4) is bonded in a 8-coordinate geometry to one O(1), one O(11), one O(14), one O(16), one O(4), one O(5), one O(8), and one I(2) atom. In the fifth Sr site, Sr(5) is bonded in a 8-coordinate geometry to one O(10), one O(11), one O(16), one O(2), one O(8), one I(2), one I(3), and one I(4) atom. In the sixth Sr site, Sr(6) is bonded in a 8-coordinate geometry to one O(1), one O(12), one O(15), one O(7), one O(9), one I(1), one I(3), and one I(4) atom. In the seventh Sr site, Sr(7) is bonded in a 8-coordinate geometry to one O(12), one O(14), one O(4), one O(6), one O(9), one I(1), one I(2), and one I(4) atom. In the eighth Sr site, Sr(8) is bonded in a 8-coordinate geometry to one O(10), one O(11), one O(13), one O(3), one O(5), one I(1), one I(2), and one I(3) atom. Mg(1) is bonded in a 3-coordinate geometry to one Sr(2), one O(14), one O(3), and one O(6) atom. There are four inequivalent P sites. In the first P site, P(1) is bonded in a tetrahedral geometry to one O(1), one O(10), one O(16), and one O(7) atom. In the second P site, P(2) is bonded in a tetrahedral geometry to one O(15), one O(2), one O(8), and one O(9) atom. In the third P site, P(3) is bonded in a tetrahedral geometry to one O(12), one O(14), one O(3), and one O(5) atom. In the fourth P site, P(4) is bonded in a tetrahedral geometry to one O(11), one O(13), one O(4), and one O(6) atom. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Sr(1), one Sr(4), one Sr(6), and one P(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Sr(2), one Sr(3), one Sr(5), and one P(2) atom. In the third O site, O(3) is bonded to one Sr(3), one Sr(8), one Mg(1), and one P(3) atom to form distorted OSr2MgP tetrahedra that share  a cornercorner with one I(3)Sr5 trigonal bipyramid. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Sr(4), one Sr(7), and one P(4) atom. In the fifth O site, O(5) is bonded in a 1-coordinate geometry to one Sr(1), one Sr(4), one Sr(8), and one P(3) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Sr(3), one Sr(7), one Mg(1), and one P(4) atom. In the seventh O site, O(7) is bonded in a 1-coordinate geometry to one Sr(2), one Sr(3), one Sr(6), and one P(1) atom. In the eighth O site, O(8) is bonded in a distorted single-bond geometry to one Sr(4), one Sr(5), and one P(2) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Sr(6), one Sr(7), and one P(2) atom. In the tenth O site, O(10) is bonded in a 1-coordinate geometry to one Sr(1), one Sr(5), one Sr(8), and one P(1) atom. In the eleventh O site, O(11) is bonded in a distorted single-bond geometry to one Sr(4), one Sr(5), one Sr(8), and one P(4) atom. In the twelfth O site, O(12) is bonded in a 2-coordinate geometry to one Sr(3), one Sr(6), one Sr(7), and one P(3) atom. In the thirteenth O site, O(13) is bonded in a distorted single-bond geometry to one Sr(1), one Sr(3), one Sr(8), and one P(4) atom. In the fourteenth O site, O(14) is bonded in a 4-coordinate geometry to one Sr(4), one Sr(7), one Mg(1), and one P(3) atom. In the fifteenth O site, O(15) is bonded in a 4-coordinate geometry to one Sr(1), one Sr(3), one Sr(6), and one P(2) atom. In the sixteenth O site, O(16) is bonded in a distorted single-bond geometry to one Sr(2), one Sr(4), one Sr(5), and one P(1) atom. There are four inequivalent I sites. In the first I site, I(1) is bonded in a 5-coordinate geometry to one Sr(2), one Sr(3), one Sr(6), one Sr(7), and one Sr(8) atom. In the second I site, I(2) is bonded in a 4-coordinate geometry to one Sr(4), one Sr(5), one Sr(7), and one Sr(8) atom. In the third I site, I(3) is bonded to one Sr(1), one Sr(2), one Sr(5), one Sr(6), and one Sr(8) atom to form ISr5 trigonal bipyramids that share  a cornercorner with one O(3)Sr2MgP tetrahedra and edges with two equivalent I(4)Sr5 trigonal bipyramids. In the fourth I site, I(4) is bonded to one Sr(1), one Sr(2), one Sr(5), one Sr(6), and one Sr(7) atom to form distorted edge-sharing ISr5 trigonal bipyramids.
Sr8MgP4(O4I)4 crystallizes in the triclinic P1 space group. There are eight inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 5-coordinate geometry to one O(1), one O(10), one O(13), one O(15), one O(5), one I(3), and one I(4) atom. The Sr(1)-O(1) bond length is 2.73 Å. The Sr(1)-O(10) bond length is 2.57 Å. The Sr(1)-O(13) bond length is 2.58 Å. The Sr(1)-O(15) bond length is 2.58 Å. The Sr(1)-O(5) bond length is 2.50 Å. The Sr(1)-I(3) bond length is 3.46 Å. The Sr(1)-I(4) bond length is 3.76 Å. In the second Sr site, Sr(2) is bonded in a 7-coordinate geometry to one Mg(1), one O(16), one O(2), one O(7), one I(1), one I(3), and one I(4) atom. The Sr(2)-Mg(1) bond length is 3.09 Å. The Sr(2)-O(16) bond length is 2.65 Å. The Sr(2)-O(2) bond length is 2.66 Å. The Sr(2)-O(7) bond length is 2.54 Å. The Sr(2)-I(1) bond length is 3.54 Å. The Sr(2)-I(3) bond length is 3.62 Å. The Sr(2)-I(4) bond length is 3.42 Å. In the third Sr site, Sr(3) is bonded in a 8-coordinate geometry to one O(12), one O(13), one O(15), one O(2), one O(3), one O(6), one O(7), and one I(1) atom. The Sr(3)-O(12) bond length is 2.97 Å. The Sr(3)-O(13) bond length is 2.61 Å. The Sr(3)-O(15) bond length is 2.51 Å. The Sr(3)-O(2) bond length is 2.75 Å. The Sr(3)-O(3) bond length is 2.56 Å. The Sr(3)-O(6) bond length is 2.67 Å. The Sr(3)-O(7) bond length is 2.52 Å. The Sr(3)-I(1) bond length is 3.63 Å. In the fourth Sr site, Sr(4) is bonded in a 8-coordinate geometry to one O(1), one O(11), one O(14), one O(16), one O(4), one O(5), one O(8), and one I(2) atom. The Sr(4)-O(1) bond length is 2.74 Å. The Sr(4)-O(11) bond length is 2.78 Å. The Sr(4)-O(14) bond length is 2.68 Å. The Sr(4)-O(16) bond length is 2.71 Å. The Sr(4)-O(4) bond length is 2.53 Å. The Sr(4)-O(5) bond length is 2.96 Å. The Sr(4)-O(8) bond length is 2.67 Å. The Sr(4)-I(2) bond length is 3.78 Å. In the fifth Sr site, Sr(5) is bonded in a 8-coordinate geometry to one O(10), one O(11), one O(16), one O(2), one O(8), one I(2), one I(3), and one I(4) atom. The Sr(5)-O(10) bond length is 3.16 Å. The Sr(5)-O(11) bond length is 2.57 Å. The Sr(5)-O(16) bond length is 2.52 Å. The Sr(5)-O(2) bond length is 2.57 Å. The Sr(5)-O(8) bond length is 2.62 Å. The Sr(5)-I(2) bond length is 3.72 Å. The Sr(5)-I(3) bond length is 3.54 Å. The Sr(5)-I(4) bond length is 3.42 Å. In the sixth Sr site, Sr(6) is bonded in a 8-coordinate geometry to one O(1), one O(12), one O(15), one O(7), one O(9), one I(1), one I(3), and one I(4) atom. The Sr(6)-O(1) bond length is 2.57 Å. The Sr(6)-O(12) bond length is 2.49 Å. The Sr(6)-O(15) bond length is 2.60 Å. The Sr(6)-O(7) bond length is 2.94 Å. The Sr(6)-O(9) bond length is 2.66 Å. The Sr(6)-I(1) bond length is 3.64 Å. The Sr(6)-I(3) bond length is 3.60 Å. The Sr(6)-I(4) bond length is 3.54 Å. In the seventh Sr site, Sr(7) is bonded in a 8-coordinate geometry to one O(12), one O(14), one O(4), one O(6), one O(9), one I(1), one I(2), and one I(4) atom. The Sr(7)-O(12) bond length is 3.06 Å. The Sr(7)-O(14) bond length is 2.53 Å. The Sr(7)-O(4) bond length is 2.50 Å. The Sr(7)-O(6) bond length is 2.70 Å. The Sr(7)-O(9) bond length is 2.48 Å. The Sr(7)-I(1) bond length is 3.41 Å. The Sr(7)-I(2) bond length is 3.67 Å. The Sr(7)-I(4) bond length is 3.48 Å. In the eighth Sr site, Sr(8) is bonded in a 8-coordinate geometry to one O(10), one O(11), one O(13), one O(3), one O(5), one I(1), one I(2), and one I(3) atom. The Sr(8)-O(10) bond length is 2.50 Å. The Sr(8)-O(11) bond length is 2.75 Å. The Sr(8)-O(13) bond length is 2.55 Å. The Sr(8)-O(3) bond length is 2.52 Å. The Sr(8)-O(5) bond length is 2.94 Å. The Sr(8)-I(1) bond length is 3.73 Å. The Sr(8)-I(2) bond length is 3.38 Å. The Sr(8)-I(3) bond length is 3.69 Å. Mg(1) is bonded in a 3-coordinate geometry to one Sr(2), one O(14), one O(3), and one O(6) atom. The Mg(1)-O(14) bond length is 2.42 Å. The Mg(1)-O(3) bond length is 2.09 Å. The Mg(1)-O(6) bond length is 2.03 Å. There are four inequivalent P sites. In the first P site, P(1) is bonded in a tetrahedral geometry to one O(1), one O(10), one O(16), and one O(7) atom. The P(1)-O(1) bond length is 1.57 Å. The P(1)-O(10) bond length is 1.55 Å. The P(1)-O(16) bond length is 1.57 Å. The P(1)-O(7) bond length is 1.55 Å. In the second P site, P(2) is bonded in a tetrahedral geometry to one O(15), one O(2), one O(8), and one O(9) atom. The P(2)-O(15) bond length is 1.58 Å. The P(2)-O(2) bond length is 1.58 Å. The P(2)-O(8) bond length is 1.55 Å. The P(2)-O(9) bond length is 1.55 Å. In the third P site, P(3) is bonded in a tetrahedral geometry to one O(12), one O(14), one O(3), and one O(5) atom. The P(3)-O(12) bond length is 1.54 Å. The P(3)-O(14) bond length is 1.57 Å. The P(3)-O(3) bond length is 1.59 Å. The P(3)-O(5) bond length is 1.54 Å. In the fourth P site, P(4) is bonded in a tetrahedral geometry to one O(11), one O(13), one O(4), and one O(6) atom. The P(4)-O(11) bond length is 1.56 Å. The P(4)-O(13) bond length is 1.56 Å. The P(4)-O(4) bond length is 1.55 Å. The P(4)-O(6) bond length is 1.56 Å. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Sr(1), one Sr(4), one Sr(6), and one P(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Sr(2), one Sr(3), one Sr(5), and one P(2) atom. In the third O site, O(3) is bonded to one Sr(3), one Sr(8), one Mg(1), and one P(3) atom to form distorted OSr2MgP tetrahedra that share  a cornercorner with one I(3)Sr5 trigonal bipyramid. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Sr(4), one Sr(7), and one P(4) atom. In the fifth O site, O(5) is bonded in a 1-coordinate geometry to one Sr(1), one Sr(4), one Sr(8), and one P(3) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Sr(3), one Sr(7), one Mg(1), and one P(4) atom. In the seventh O site, O(7) is bonded in a 1-coordinate geometry to one Sr(2), one Sr(3), one Sr(6), and one P(1) atom. In the eighth O site, O(8) is bonded in a distorted single-bond geometry to one Sr(4), one Sr(5), and one P(2) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Sr(6), one Sr(7), and one P(2) atom. In the tenth O site, O(10) is bonded in a 1-coordinate geometry to one Sr(1), one Sr(5), one Sr(8), and one P(1) atom. In the eleventh O site, O(11) is bonded in a distorted single-bond geometry to one Sr(4), one Sr(5), one Sr(8), and one P(4) atom. In the twelfth O site, O(12) is bonded in a 2-coordinate geometry to one Sr(3), one Sr(6), one Sr(7), and one P(3) atom. In the thirteenth O site, O(13) is bonded in a distorted single-bond geometry to one Sr(1), one Sr(3), one Sr(8), and one P(4) atom. In the fourteenth O site, O(14) is bonded in a 4-coordinate geometry to one Sr(4), one Sr(7), one Mg(1), and one P(3) atom. In the fifteenth O site, O(15) is bonded in a 4-coordinate geometry to one Sr(1), one Sr(3), one Sr(6), and one P(2) atom. In the sixteenth O site, O(16) is bonded in a distorted single-bond geometry to one Sr(2), one Sr(4), one Sr(5), and one P(1) atom. There are four inequivalent I sites. In the first I site, I(1) is bonded in a 5-coordinate geometry to one Sr(2), one Sr(3), one Sr(6), one Sr(7), and one Sr(8) atom. In the second I site, I(2) is bonded in a 4-coordinate geometry to one Sr(4), one Sr(5), one Sr(7), and one Sr(8) atom. In the third I site, I(3) is bonded to one Sr(1), one Sr(2), one Sr(5), one Sr(6), and one Sr(8) atom to form ISr5 trigonal bipyramids that share  a cornercorner with one O(3)Sr2MgP tetrahedra and edges with two equivalent I(4)Sr5 trigonal bipyramids. In the fourth I site, I(4) is bonded to one Sr(1), one Sr(2), one Sr(5), one Sr(6), and one Sr(7) atom to form distorted edge-sharing ISr5 trigonal bipyramids.