K2Ca3Si3O10 crystallizes in the monoclinic C2/c space group. K(1) is bonded in a 10-coordinate geometry to one O(4), two equivalent O(1), two equivalent O(3), two equivalent O(5), and three equivalent O(2) atoms. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form CaO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra. In the second Ca site, Ca(2) is bonded in a 7-coordinate geometry to one O(1), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. There are two inequivalent Si sites. In the first Si site, 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(1)O6 octahedra and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 12-44°. In the second Si site, Si(2) is bonded to two equivalent O(2) and two equivalent O(5) atoms to form corner-sharing SiO4 tetrahedra. There are five inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to two equivalent K(1), one Ca(1), one Ca(2), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to three equivalent K(1), one Si(1), and one Si(2) atom. In the third O site, O(3) is bonded in a 6-coordinate geometry to two equivalent K(1), one Ca(1), two equivalent Ca(2), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 1-coordinate geometry to one K(1), one Ca(1), two equivalent Ca(2), and one Si(1) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to two equivalent K(1), two equivalent Ca(2), and one Si(2) atom.
K2Ca3Si3O10 crystallizes in the monoclinic C2/c space group. K(1) is bonded in a 10-coordinate geometry to one O(4), two equivalent O(1), two equivalent O(3), two equivalent O(5), and three equivalent O(2) atoms. The K(1)-O(4) bond length is 3.11 Å. There is one shorter (2.74 Å) and one longer (2.91 Å) K(1)-O(1) bond length. There is one shorter (2.89 Å) and one longer (2.90 Å) K(1)-O(3) bond length. There is one shorter (2.84 Å) and one longer (3.33 Å) K(1)-O(5) bond length. There are a spread of K(1)-O(2) bond distances ranging from 2.74-3.22 Å. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form CaO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra. Both Ca(1)-O(1) bond lengths are 2.36 Å. Both Ca(1)-O(3) bond lengths are 2.38 Å. Both Ca(1)-O(4) bond lengths are 2.41 Å. In the second Ca site, Ca(2) is bonded in a 7-coordinate geometry to one O(1), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. The Ca(2)-O(1) bond length is 2.81 Å. There is one shorter (2.56 Å) and one longer (2.69 Å) Ca(2)-O(3) bond length. There is one shorter (2.37 Å) and one longer (2.67 Å) Ca(2)-O(4) bond length. There is one shorter (2.27 Å) and one longer (2.43 Å) Ca(2)-O(5) bond length. There are two inequivalent Si sites. In the first Si site, 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(1)O6 octahedra and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 12-44°. The Si(1)-O(1) bond length is 1.63 Å. The Si(1)-O(2) bond length is 1.69 Å. The Si(1)-O(3) bond length is 1.66 Å. The Si(1)-O(4) bond length is 1.63 Å. In the second Si site, Si(2) is bonded to two equivalent O(2) and two equivalent O(5) atoms to form corner-sharing SiO4 tetrahedra. Both Si(2)-O(2) bond lengths are 1.67 Å. Both Si(2)-O(5) bond lengths are 1.61 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to two equivalent K(1), one Ca(1), one Ca(2), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to three equivalent K(1), one Si(1), and one Si(2) atom. In the third O site, O(3) is bonded in a 6-coordinate geometry to two equivalent K(1), one Ca(1), two equivalent Ca(2), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 1-coordinate geometry to one K(1), one Ca(1), two equivalent Ca(2), and one Si(1) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to two equivalent K(1), two equivalent Ca(2), and one Si(2) atom.