K3U3Si2O13 is Pb(Zr_(1-x)Ti_x)O3-derived structured and crystallizes in the hexagonal P-62c space group. K(1) is bonded in a 11-coordinate geometry to one O(4), two equivalent O(1), two equivalent O(3), and six equivalent O(2) atoms. U(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form UO6 octahedra that share corners with four equivalent U(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 5-36°. Si(1) is bonded to one O(4) and three equivalent O(2) atoms to form SiO4 tetrahedra that share corners with three equivalent U(1)O6 octahedra and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 25°. There are four inequivalent O sites. In the first O site, O(4) is bonded in a linear geometry to three equivalent K(1) and two equivalent Si(1) atoms. In the second O site, O(1) is bonded in a linear geometry to two equivalent K(1) and two equivalent U(1) atoms. In the third O site, O(2) is bonded in a 2-coordinate geometry to three equivalent K(1), one U(1), and one Si(1) atom. In the fourth O site, O(3) is bonded in a 4-coordinate geometry to two equivalent K(1) and two equivalent U(1) atoms.
K3U3Si2O13 is Pb(Zr_(1-x)Ti_x)O3-derived structured and crystallizes in the hexagonal P-62c space group. K(1) is bonded in a 11-coordinate geometry to one O(4), two equivalent O(1), two equivalent O(3), and six equivalent O(2) atoms. The K(1)-O(4) bond length is 3.26 Å. There is one shorter (3.22 Å) and one longer (3.31 Å) K(1)-O(1) bond length. Both K(1)-O(3) bond lengths are 2.98 Å. There are a spread of K(1)-O(2) bond distances ranging from 2.93-3.35 Å. U(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form UO6 octahedra that share corners with four equivalent U(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 5-36°. Both U(1)-O(1) bond lengths are 2.12 Å. Both U(1)-O(2) bond lengths are 2.22 Å. Both U(1)-O(3) bond lengths are 2.15 Å. Si(1) is bonded to one O(4) and three equivalent O(2) atoms to form SiO4 tetrahedra that share corners with three equivalent U(1)O6 octahedra and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 25°. The Si(1)-O(4) bond length is 1.65 Å. All Si(1)-O(2) bond lengths are 1.63 Å. There are four inequivalent O sites. In the first O site, O(4) is bonded in a linear geometry to three equivalent K(1) and two equivalent Si(1) atoms. In the second O site, O(1) is bonded in a linear geometry to two equivalent K(1) and two equivalent U(1) atoms. In the third O site, O(2) is bonded in a 2-coordinate geometry to three equivalent K(1), one U(1), and one Si(1) atom. In the fourth O site, O(3) is bonded in a 4-coordinate geometry to two equivalent K(1) and two equivalent U(1) atoms.