CaCu(SiO3)2 is Esseneite structured and crystallizes in the monoclinic C2/c space group. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), and four equivalent O(1) atoms. Cu(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form CuO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra and edges with two equivalent Cu(1)O6 octahedra. Si(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form SiO4 tetrahedra that share corners with three equivalent Cu(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 36-58°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to two equivalent Ca(1) and two equivalent Si(1) atoms. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Ca(1), one Cu(1), and one Si(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ca(1), two equivalent Cu(1), and one Si(1) atom.
CaCu(SiO3)2 is Esseneite structured and crystallizes in the monoclinic C2/c space group. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), and four equivalent O(1) atoms. Both Ca(1)-O(2) bond lengths are 2.34 Å. Both Ca(1)-O(3) bond lengths are 2.36 Å. There are two shorter (2.64 Å) and two longer (2.78 Å) Ca(1)-O(1) bond lengths. Cu(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form CuO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra and edges with two equivalent Cu(1)O6 octahedra. Both Cu(1)-O(2) bond lengths are 2.09 Å. There are two shorter (2.05 Å) and two longer (2.18 Å) Cu(1)-O(3) bond lengths. Si(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form SiO4 tetrahedra that share corners with three equivalent Cu(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 36-58°. The Si(1)-O(2) bond length is 1.60 Å. The Si(1)-O(3) bond length is 1.63 Å. There is one shorter (1.68 Å) and one longer (1.70 Å) Si(1)-O(1) bond length. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to two equivalent Ca(1) and two equivalent Si(1) atoms. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Ca(1), one Cu(1), and one Si(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ca(1), two equivalent Cu(1), and one Si(1) atom.