Rb2Ca2(SiO3)3 crystallizes in the monoclinic Pc space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 3-coordinate geometry to one O(2), one O(3), and one O(6) atom. In the second Rb site, Rb(2) is bonded in a 7-coordinate geometry to one O(2), one O(4), one O(6), one O(7), one O(8), and two equivalent O(3) atoms. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(1), one O(3), one O(4), one O(5), and one O(7) atom to form distorted CaO5 trigonal bipyramids that share  a cornercorner with one Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, and edges with two equivalent Ca(2)O5 trigonal bipyramids. In the second Ca site, Ca(2) is bonded to one O(1), one O(4), one O(5), one O(6), and one O(7) atom to form distorted CaO5 trigonal bipyramids that share  a cornercorner with one Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, and edges with two equivalent Ca(1)O5 trigonal bipyramids. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(3), one O(6), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra,  a cornercorner with one Ca(1)O5 trigonal bipyramid, and  a cornercorner with one Ca(2)O5 trigonal bipyramid. In the second Si site, Si(2) is bonded to one O(1), one O(2), one O(5), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, corners with two equivalent Ca(1)O5 trigonal bipyramids, and corners with two equivalent Ca(2)O5 trigonal bipyramids. In the third Si site, Si(3) is bonded to one O(4), one O(7), one O(8), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Ca(1)O5 trigonal bipyramids, and corners with two equivalent Ca(2)O5 trigonal bipyramids. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(2), and one Si(2) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Rb(1), one Rb(2), one Si(1), and one Si(2) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to one Rb(1), two equivalent Rb(2), one Ca(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Rb(2), one Ca(1), one Ca(2), and one Si(3) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(2), and one Si(2) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Rb(1), one Rb(2), one Ca(2), and one Si(1) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Rb(2), one Ca(1), one Ca(2), and one Si(3) atom. In the eighth O site, O(8) is bonded in a 2-coordinate geometry to one Rb(2), one Si(2), and one Si(3) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(3) atom.
Rb2Ca2(SiO3)3 crystallizes in the monoclinic Pc space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 3-coordinate geometry to one O(2), one O(3), and one O(6) atom. The Rb(1)-O(2) bond length is 2.83 Å. The Rb(1)-O(3) bond length is 2.82 Å. The Rb(1)-O(6) bond length is 2.87 Å. In the second Rb site, Rb(2) is bonded in a 7-coordinate geometry to one O(2), one O(4), one O(6), one O(7), one O(8), and two equivalent O(3) atoms. The Rb(2)-O(2) bond length is 3.30 Å. The Rb(2)-O(4) bond length is 3.00 Å. The Rb(2)-O(6) bond length is 2.98 Å. The Rb(2)-O(7) bond length is 3.28 Å. The Rb(2)-O(8) bond length is 2.92 Å. There is one shorter (3.21 Å) and one longer (3.43 Å) Rb(2)-O(3) bond length. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(1), one O(3), one O(4), one O(5), and one O(7) atom to form distorted CaO5 trigonal bipyramids that share  a cornercorner with one Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, and edges with two equivalent Ca(2)O5 trigonal bipyramids. The Ca(1)-O(1) bond length is 2.35 Å. The Ca(1)-O(3) bond length is 2.29 Å. The Ca(1)-O(4) bond length is 2.36 Å. The Ca(1)-O(5) bond length is 2.32 Å. The Ca(1)-O(7) bond length is 2.33 Å. In the second Ca site, Ca(2) is bonded to one O(1), one O(4), one O(5), one O(6), and one O(7) atom to form distorted CaO5 trigonal bipyramids that share  a cornercorner with one Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, and edges with two equivalent Ca(1)O5 trigonal bipyramids. The Ca(2)-O(1) bond length is 2.29 Å. The Ca(2)-O(4) bond length is 2.30 Å. The Ca(2)-O(5) bond length is 2.32 Å. The Ca(2)-O(6) bond length is 2.22 Å. The Ca(2)-O(7) bond length is 2.40 Å. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(3), one O(6), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra,  a cornercorner with one Ca(1)O5 trigonal bipyramid, and  a cornercorner with one Ca(2)O5 trigonal bipyramid. The Si(1)-O(2) bond length is 1.69 Å. The Si(1)-O(3) bond length is 1.62 Å. The Si(1)-O(6) bond length is 1.62 Å. The Si(1)-O(9) bond length is 1.68 Å. In the second Si site, Si(2) is bonded to one O(1), one O(2), one O(5), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, corners with two equivalent Ca(1)O5 trigonal bipyramids, and corners with two equivalent Ca(2)O5 trigonal bipyramids. The Si(2)-O(1) bond length is 1.62 Å. The Si(2)-O(2) bond length is 1.67 Å. The Si(2)-O(5) bond length is 1.61 Å. The Si(2)-O(8) bond length is 1.69 Å. In the third Si site, Si(3) is bonded to one O(4), one O(7), one O(8), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Ca(1)O5 trigonal bipyramids, and corners with two equivalent Ca(2)O5 trigonal bipyramids. The Si(3)-O(4) bond length is 1.62 Å. The Si(3)-O(7) bond length is 1.63 Å. The Si(3)-O(8) bond length is 1.69 Å. The Si(3)-O(9) bond length is 1.66 Å. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(2), and one Si(2) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Rb(1), one Rb(2), one Si(1), and one Si(2) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to one Rb(1), two equivalent Rb(2), one Ca(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Rb(2), one Ca(1), one Ca(2), and one Si(3) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(2), and one Si(2) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Rb(1), one Rb(2), one Ca(2), and one Si(1) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Rb(2), one Ca(1), one Ca(2), and one Si(3) atom. In the eighth O site, O(8) is bonded in a 2-coordinate geometry to one Rb(2), one Si(2), and one Si(3) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(3) atom.