SrMn2Si2(H2O5)2 crystallizes in the monoclinic P2_1/m space group. Sr(1) is bonded in a 8-coordinate geometry to one O(1), one O(6), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms to form MnO6 octahedra that share corners with four equivalent Si(1)O4 tetrahedra and edges with two equivalent Mn(2)O6 octahedra. In the second Mn site, Mn(2) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms to form MnO6 octahedra that share corners with four equivalent Si(1)O4 tetrahedra and edges with two equivalent Mn(1)O6 octahedra. Si(1) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form SiO4 tetrahedra that share corners with two equivalent Mn(1)O6 octahedra, corners with two equivalent Mn(2)O6 octahedra, and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 47-59°. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(6) atom. In the second H site, H(2) is bonded in a single-bond geometry to one O(2) atom. There are six inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to one Sr(1), one Mn(1), one Mn(2), and one Si(1) atom. In the second O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Sr(1) and two equivalent H(1) atoms. In the third O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Sr(1) and two equivalent Si(1) atoms. In the fourth O site, O(2) is bonded in a distorted single-bond geometry to one Mn(1), one Mn(2), and one H(2) atom. In the fifth O site, O(3) is bonded in a distorted trigonal planar geometry to one Sr(1), one Mn(1), and one Si(1) atom. In the sixth O site, O(4) is bonded in a distorted trigonal planar geometry to one Sr(1), one Mn(2), and one Si(1) atom.
SrMn2Si2(H2O5)2 crystallizes in the monoclinic P2_1/m space group. Sr(1) is bonded in a 8-coordinate geometry to one O(1), one O(6), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. The Sr(1)-O(1) bond length is 2.70 Å. The Sr(1)-O(6) bond length is 2.60 Å. Both Sr(1)-O(3) bond lengths are 2.65 Å. Both Sr(1)-O(4) bond lengths are 2.63 Å. Both Sr(1)-O(5) bond lengths are 2.87 Å. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms to form MnO6 octahedra that share corners with four equivalent Si(1)O4 tetrahedra and edges with two equivalent Mn(2)O6 octahedra. Both Mn(1)-O(2) bond lengths are 2.02 Å. Both Mn(1)-O(3) bond lengths are 1.95 Å. Both Mn(1)-O(5) bond lengths are 2.17 Å. In the second Mn site, Mn(2) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms to form MnO6 octahedra that share corners with four equivalent Si(1)O4 tetrahedra and edges with two equivalent Mn(1)O6 octahedra. Both Mn(2)-O(2) bond lengths are 2.00 Å. Both Mn(2)-O(4) bond lengths are 1.95 Å. Both Mn(2)-O(5) bond lengths are 2.21 Å. Si(1) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form SiO4 tetrahedra that share corners with two equivalent Mn(1)O6 octahedra, corners with two equivalent Mn(2)O6 octahedra, and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 47-59°. The Si(1)-O(1) bond length is 1.66 Å. The Si(1)-O(3) bond length is 1.65 Å. The Si(1)-O(4) bond length is 1.65 Å. The Si(1)-O(5) bond length is 1.63 Å. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(6) atom. The H(1)-O(6) bond length is 0.99 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(2) atom. The H(2)-O(2) bond length is 0.98 Å. There are six inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to one Sr(1), one Mn(1), one Mn(2), and one Si(1) atom. In the second O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Sr(1) and two equivalent H(1) atoms. In the third O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Sr(1) and two equivalent Si(1) atoms. In the fourth O site, O(2) is bonded in a distorted single-bond geometry to one Mn(1), one Mn(2), and one H(2) atom. In the fifth O site, O(3) is bonded in a distorted trigonal planar geometry to one Sr(1), one Mn(1), and one Si(1) atom. In the sixth O site, O(4) is bonded in a distorted trigonal planar geometry to one Sr(1), one Mn(2), and one Si(1) atom.