Ca3(SiO5)2 crystallizes in the monoclinic Cc space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 6-coordinate geometry to one O(2), one O(4), one O(5), one O(6), one O(7), and one O(8) atom. In the second Ca site, Ca(2) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(5), one O(7), and one O(8) atom. In the third Ca site, Ca(3) is bonded in a 7-coordinate geometry to one O(10), one O(2), one O(5), one O(6), one O(7), one O(8), and one O(9) atom. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a tetrahedral geometry to one O(1), one O(4), one O(7), and one O(8) atom. In the second Si site, Si(2) is bonded in a tetrahedral geometry to one O(2), one O(3), one O(5), and one O(6) atom. There are ten inequivalent O sites. In the first O site, O(7) is bonded to one Ca(1), one Ca(2), one Ca(3), and one Si(1) atom to form distorted corner-sharing OCa3Si tetrahedra. In the second O site, O(8) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Ca(3), and one Si(1) atom. In the third O site, O(9) is bonded in a bent 150 degrees geometry to one Ca(3) and one O(10) atom. In the fourth O site, O(10) is bonded in a distorted bent 150 degrees geometry to one Ca(3) and one O(9) atom. In the fifth O site, O(1) is bonded in a bent 150 degrees geometry to one Ca(2) and one Si(1) atom. In the sixth O site, O(2) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(3), and one Si(2) atom. In the seventh O site, O(3) is bonded in a bent 120 degrees geometry to one Ca(2) and one Si(2) atom. In the eighth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one Ca(1) and one Si(1) atom. In the ninth O site, O(5) is bonded to one Ca(1), one Ca(2), one Ca(3), and one Si(2) atom to form distorted corner-sharing OCa3Si tetrahedra. In the tenth O site, O(6) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(3), and one Si(2) atom.
Ca3(SiO5)2 crystallizes in the monoclinic Cc space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 6-coordinate geometry to one O(2), one O(4), one O(5), one O(6), one O(7), and one O(8) atom. The Ca(1)-O(2) bond length is 2.34 Å. The Ca(1)-O(4) bond length is 2.34 Å. The Ca(1)-O(5) bond length is 2.31 Å. The Ca(1)-O(6) bond length is 2.43 Å. The Ca(1)-O(7) bond length is 2.42 Å. The Ca(1)-O(8) bond length is 2.72 Å. In the second Ca site, Ca(2) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(5), one O(7), and one O(8) atom. The Ca(2)-O(1) bond length is 2.33 Å. The Ca(2)-O(3) bond length is 2.31 Å. The Ca(2)-O(5) bond length is 2.37 Å. The Ca(2)-O(7) bond length is 2.32 Å. The Ca(2)-O(8) bond length is 2.39 Å. In the third Ca site, Ca(3) is bonded in a 7-coordinate geometry to one O(10), one O(2), one O(5), one O(6), one O(7), one O(8), and one O(9) atom. The Ca(3)-O(10) bond length is 2.90 Å. The Ca(3)-O(2) bond length is 2.54 Å. The Ca(3)-O(5) bond length is 2.33 Å. The Ca(3)-O(6) bond length is 2.33 Å. The Ca(3)-O(7) bond length is 2.34 Å. The Ca(3)-O(8) bond length is 2.33 Å. The Ca(3)-O(9) bond length is 2.77 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a tetrahedral geometry to one O(1), one O(4), one O(7), and one O(8) atom. The Si(1)-O(1) bond length is 1.65 Å. The Si(1)-O(4) bond length is 1.65 Å. The Si(1)-O(7) bond length is 1.65 Å. The Si(1)-O(8) bond length is 1.64 Å. In the second Si site, Si(2) is bonded in a tetrahedral geometry to one O(2), one O(3), one O(5), and one O(6) atom. The Si(2)-O(2) bond length is 1.64 Å. The Si(2)-O(3) bond length is 1.65 Å. The Si(2)-O(5) bond length is 1.65 Å. The Si(2)-O(6) bond length is 1.64 Å. There are ten inequivalent O sites. In the first O site, O(7) is bonded to one Ca(1), one Ca(2), one Ca(3), and one Si(1) atom to form distorted corner-sharing OCa3Si tetrahedra. In the second O site, O(8) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Ca(3), and one Si(1) atom. In the third O site, O(9) is bonded in a bent 150 degrees geometry to one Ca(3) and one O(10) atom. The O(9)-O(10) bond length is 1.24 Å. In the fourth O site, O(10) is bonded in a distorted bent 150 degrees geometry to one Ca(3) and one O(9) atom. In the fifth O site, O(1) is bonded in a bent 150 degrees geometry to one Ca(2) and one Si(1) atom. In the sixth O site, O(2) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(3), and one Si(2) atom. In the seventh O site, O(3) is bonded in a bent 120 degrees geometry to one Ca(2) and one Si(2) atom. In the eighth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one Ca(1) and one Si(1) atom. In the ninth O site, O(5) is bonded to one Ca(1), one Ca(2), one Ca(3), and one Si(2) atom to form distorted corner-sharing OCa3Si tetrahedra. In the tenth O site, O(6) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(3), and one Si(2) atom.