Ca2SiO4 crystallizes in the monoclinic C2 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), two equivalent O(1), and two equivalent O(3) atoms. In the second Ca site, Ca(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form CaO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra. In the third Ca site, Ca(3) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share corners with three equivalent Ca(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 14-44°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 1-coordinate geometry to one Ca(2), one Ca(3), two equivalent Ca(1), and one Si(1) atom. In the second O site, O(2) 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(3) is bonded in a 5-coordinate geometry to one Ca(2), one Ca(3), two equivalent Ca(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(3), and one Si(1) atom.
Ca2SiO4 crystallizes in the monoclinic C2 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), two equivalent O(1), and two equivalent O(3) atoms. The Ca(1)-O(2) bond length is 2.34 Å. The Ca(1)-O(4) bond length is 2.17 Å. There is one shorter (2.50 Å) and one longer (2.82 Å) Ca(1)-O(1) bond length. There is one shorter (2.59 Å) and one longer (2.82 Å) Ca(1)-O(3) bond length. In the second Ca site, Ca(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form CaO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra. Both Ca(2)-O(1) bond lengths are 2.27 Å. Both Ca(2)-O(2) bond lengths are 2.39 Å. Both Ca(2)-O(3) bond lengths are 2.26 Å. In the third Ca site, Ca(3) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. Both Ca(3)-O(1) bond lengths are 2.87 Å. Both Ca(3)-O(2) bond lengths are 2.50 Å. Both Ca(3)-O(3) bond lengths are 2.76 Å. Both Ca(3)-O(4) bond lengths are 2.37 Å. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share corners with three equivalent Ca(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 14-44°. The Si(1)-O(1) bond length is 1.66 Å. The Si(1)-O(2) bond length is 1.66 Å. The Si(1)-O(3) bond length is 1.67 Å. The Si(1)-O(4) bond length is 1.62 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 1-coordinate geometry to one Ca(2), one Ca(3), two equivalent Ca(1), and one Si(1) atom. In the second O site, O(2) 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(3) is bonded in a 5-coordinate geometry to one Ca(2), one Ca(3), two equivalent Ca(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(3), and one Si(1) atom.