Ba2P7I crystallizes in the monoclinic P2_1/m space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 11-coordinate geometry to one P(2), two equivalent P(5), four equivalent P(4), and four equivalent I(1) atoms. In the second Ba site, Ba(2) is bonded in a 9-coordinate geometry to one P(1), two equivalent P(4), two equivalent P(5), three equivalent P(3), and one I(1) atom. There are five inequivalent P sites. In the first P site, P(1) is bonded in a 4-coordinate geometry to one Ba(2), one P(3), and two equivalent P(5) atoms. In the second P site, P(2) is bonded to one Ba(1), one P(3), and two equivalent P(4) atoms to form PBaP3 tetrahedra that share corners with four equivalent I(1)Ba5 square pyramids and corners with four equivalent P(4)Ba3P2 trigonal bipyramids. In the third P site, P(3) is bonded to three equivalent Ba(2), one P(1), and one P(2) atom to form distorted PBa3P2 square pyramids that share corners with two equivalent P(3)Ba3P2 square pyramids, corners with three equivalent I(1)Ba5 square pyramids, corners with four equivalent P(4)Ba3P2 trigonal bipyramids, edges with two equivalent P(3)Ba3P2 square pyramids, and edges with two equivalent P(4)Ba3P2 trigonal bipyramids. In the fourth P site, P(4) is bonded to one Ba(2), two equivalent Ba(1), one P(2), and one P(5) atom to form PBa3P2 trigonal bipyramids that share corners with two equivalent P(3)Ba3P2 square pyramids, corners with three equivalent I(1)Ba5 square pyramids, corners with two equivalent P(2)BaP3 tetrahedra, corners with two equivalent P(4)Ba3P2 trigonal bipyramids,  an edgeedge with one P(3)Ba3P2 square pyramid, edges with three equivalent I(1)Ba5 square pyramids, and edges with three equivalent P(4)Ba3P2 trigonal bipyramids. In the fifth P site, P(5) is bonded in a 5-coordinate geometry to one Ba(1), one Ba(2), one P(1), one P(4), and one P(5) atom. I(1) is bonded to one Ba(2) and four equivalent Ba(1) atoms to form distorted IBa5 square pyramids that share corners with three equivalent P(3)Ba3P2 square pyramids, corners with four equivalent I(1)Ba5 square pyramids, corners with four equivalent P(2)BaP3 tetrahedra, corners with six equivalent P(4)Ba3P2 trigonal bipyramids, edges with four equivalent I(1)Ba5 square pyramids, and edges with six equivalent P(4)Ba3P2 trigonal bipyramids.
Ba2P7I crystallizes in the monoclinic P2_1/m space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 11-coordinate geometry to one P(2), two equivalent P(5), four equivalent P(4), and four equivalent I(1) atoms. The Ba(1)-P(2) bond length is 3.52 Å. Both Ba(1)-P(5) bond lengths are 3.50 Å. There are two shorter (3.41 Å) and two longer (3.54 Å) Ba(1)-P(4) bond lengths. There are a spread of Ba(1)-I(1) bond distances ranging from 3.53-3.71 Å. In the second Ba site, Ba(2) is bonded in a 9-coordinate geometry to one P(1), two equivalent P(4), two equivalent P(5), three equivalent P(3), and one I(1) atom. The Ba(2)-P(1) bond length is 3.42 Å. Both Ba(2)-P(4) bond lengths are 3.38 Å. Both Ba(2)-P(5) bond lengths are 3.70 Å. There is one shorter (3.39 Å) and two longer (3.59 Å) Ba(2)-P(3) bond lengths. The Ba(2)-I(1) bond length is 3.53 Å. There are five inequivalent P sites. In the first P site, P(1) is bonded in a 4-coordinate geometry to one Ba(2), one P(3), and two equivalent P(5) atoms. The P(1)-P(3) bond length is 2.15 Å. Both P(1)-P(5) bond lengths are 2.23 Å. In the second P site, P(2) is bonded to one Ba(1), one P(3), and two equivalent P(4) atoms to form PBaP3 tetrahedra that share corners with four equivalent I(1)Ba5 square pyramids and corners with four equivalent P(4)Ba3P2 trigonal bipyramids. The P(2)-P(3) bond length is 2.18 Å. Both P(2)-P(4) bond lengths are 2.18 Å. In the third P site, P(3) is bonded to three equivalent Ba(2), one P(1), and one P(2) atom to form distorted PBa3P2 square pyramids that share corners with two equivalent P(3)Ba3P2 square pyramids, corners with three equivalent I(1)Ba5 square pyramids, corners with four equivalent P(4)Ba3P2 trigonal bipyramids, edges with two equivalent P(3)Ba3P2 square pyramids, and edges with two equivalent P(4)Ba3P2 trigonal bipyramids. In the fourth P site, P(4) is bonded to one Ba(2), two equivalent Ba(1), one P(2), and one P(5) atom to form PBa3P2 trigonal bipyramids that share corners with two equivalent P(3)Ba3P2 square pyramids, corners with three equivalent I(1)Ba5 square pyramids, corners with two equivalent P(2)BaP3 tetrahedra, corners with two equivalent P(4)Ba3P2 trigonal bipyramids,  an edgeedge with one P(3)Ba3P2 square pyramid, edges with three equivalent I(1)Ba5 square pyramids, and edges with three equivalent P(4)Ba3P2 trigonal bipyramids. The P(4)-P(5) bond length is 2.14 Å. In the fifth P site, P(5) is bonded in a 5-coordinate geometry to one Ba(1), one Ba(2), one P(1), one P(4), and one P(5) atom. The P(5)-P(5) bond length is 2.33 Å. I(1) is bonded to one Ba(2) and four equivalent Ba(1) atoms to form distorted IBa5 square pyramids that share corners with three equivalent P(3)Ba3P2 square pyramids, corners with four equivalent I(1)Ba5 square pyramids, corners with four equivalent P(2)BaP3 tetrahedra, corners with six equivalent P(4)Ba3P2 trigonal bipyramids, edges with four equivalent I(1)Ba5 square pyramids, and edges with six equivalent P(4)Ba3P2 trigonal bipyramids.