Mn2Si(H2O3)2 crystallizes in the orthorhombic Pca2_1 space group. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form MnO6 octahedra that share  a cornercorner with one Mn(2)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, edges with two equivalent Mn(1)O6 octahedra, and edges with three equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles are 55°. In the second Mn site, Mn(2) is bonded to one O(1), one O(3), one O(4), one O(5), and two equivalent O(2) atoms to form distorted MnO6 octahedra that share  a cornercorner with one Mn(1)O6 octahedra, corners with two equivalent Mn(2)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, and edges with three equivalent Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-56°. Si(1) is bonded to one O(1), one O(5), and two equivalent O(6) atoms to form SiO4 tetrahedra that share corners with two equivalent Mn(1)O6 octahedra, corners with two equivalent Mn(2)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 58-62°. There are four inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(2) atom. In the second H site, H(2) is bonded in a single-bond geometry to one O(3) atom. In the third H site, H(3) is bonded in a linear geometry to one O(4) and one O(5) atom. In the fourth H site, H(4) is bonded in a distorted single-bond geometry to one O(4) and one O(5) atom. There are six inequivalent O sites. In the first O site, O(2) is bonded in a distorted single-bond geometry to one Mn(1), two equivalent Mn(2), and one H(1) atom. In the second O site, O(3) is bonded in a distorted single-bond geometry to one Mn(2), two equivalent Mn(1), and one H(2) atom. In the third O site, O(4) is bonded in a distorted water-like geometry to one Mn(1), one Mn(2), one H(3), and one H(4) atom. In the fourth O site, O(5) is bonded in a distorted tetrahedral geometry to one Mn(2), one Si(1), one H(3), and one H(4) atom. In the fifth O site, O(6) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the sixth O site, O(1) is bonded in a 4-coordinate geometry to one Mn(2), two equivalent Mn(1), and one Si(1) atom.
Mn2Si(H2O3)2 crystallizes in the orthorhombic Pca2_1 space group. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form MnO6 octahedra that share  a cornercorner with one Mn(2)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, edges with two equivalent Mn(1)O6 octahedra, and edges with three equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles are 55°. The Mn(1)-O(2) bond length is 2.24 Å. The Mn(1)-O(4) bond length is 2.30 Å. There is one shorter (2.15 Å) and one longer (2.28 Å) Mn(1)-O(1) bond length. There is one shorter (2.15 Å) and one longer (2.18 Å) Mn(1)-O(3) bond length. In the second Mn site, Mn(2) is bonded to one O(1), one O(3), one O(4), one O(5), and two equivalent O(2) atoms to form distorted MnO6 octahedra that share  a cornercorner with one Mn(1)O6 octahedra, corners with two equivalent Mn(2)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, and edges with three equivalent Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-56°. The Mn(2)-O(1) bond length is 2.41 Å. The Mn(2)-O(3) bond length is 2.18 Å. The Mn(2)-O(4) bond length is 2.31 Å. The Mn(2)-O(5) bond length is 2.26 Å. There is one shorter (2.14 Å) and one longer (2.18 Å) Mn(2)-O(2) bond length. Si(1) is bonded to one O(1), one O(5), and two equivalent O(6) atoms to form SiO4 tetrahedra that share corners with two equivalent Mn(1)O6 octahedra, corners with two equivalent Mn(2)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 58-62°. The Si(1)-O(1) bond length is 1.63 Å. The Si(1)-O(5) bond length is 1.63 Å. Both Si(1)-O(6) bond lengths are 1.69 Å. There are four inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(2) atom. The H(1)-O(2) bond length is 0.98 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(3) atom. The H(2)-O(3) bond length is 0.98 Å. In the third H site, H(3) is bonded in a linear geometry to one O(4) and one O(5) atom. The H(3)-O(4) bond length is 1.03 Å. The H(3)-O(5) bond length is 1.57 Å. In the fourth H site, H(4) is bonded in a distorted single-bond geometry to one O(4) and one O(5) atom. The H(4)-O(4) bond length is 1.01 Å. The H(4)-O(5) bond length is 1.69 Å. There are six inequivalent O sites. In the first O site, O(2) is bonded in a distorted single-bond geometry to one Mn(1), two equivalent Mn(2), and one H(1) atom. In the second O site, O(3) is bonded in a distorted single-bond geometry to one Mn(2), two equivalent Mn(1), and one H(2) atom. In the third O site, O(4) is bonded in a distorted water-like geometry to one Mn(1), one Mn(2), one H(3), and one H(4) atom. In the fourth O site, O(5) is bonded in a distorted tetrahedral geometry to one Mn(2), one Si(1), one H(3), and one H(4) atom. In the fifth O site, O(6) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the sixth O site, O(1) is bonded in a 4-coordinate geometry to one Mn(2), two equivalent Mn(1), and one Si(1) atom.