Cs2KU2(Si2O7)2 crystallizes in the orthorhombic Cmmm space group. Cs(1) is bonded in a 6-coordinate geometry to two equivalent O(4) and four equivalent O(3) atoms. K(1) is bonded in a distorted q6 geometry to two equivalent O(1) and eight equivalent O(3) atoms. U(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form UO6 octahedra that share corners with two equivalent U(1)O6 octahedra and corners with four equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 1°. Si(1) is bonded to one O(2), one O(4), and two equivalent O(3) atoms to form SiO4 tetrahedra that share corners with two equivalent U(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 29°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to one K(1) and two equivalent U(1) atoms. In the second O site, O(2) is bonded in a linear geometry to two equivalent Si(1) atoms. In the third O site, O(3) is bonded in a 2-coordinate geometry to one Cs(1), one K(1), one U(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to two equivalent Cs(1) and two equivalent Si(1) atoms.
Cs2KU2(Si2O7)2 crystallizes in the orthorhombic Cmmm space group. Cs(1) is bonded in a 6-coordinate geometry to two equivalent O(4) and four equivalent O(3) atoms. Both Cs(1)-O(4) bond lengths are 3.33 Å. All Cs(1)-O(3) bond lengths are 3.29 Å. K(1) is bonded in a distorted q6 geometry to two equivalent O(1) and eight equivalent O(3) atoms. Both K(1)-O(1) bond lengths are 2.93 Å. All K(1)-O(3) bond lengths are 2.93 Å. U(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form UO6 octahedra that share corners with two equivalent U(1)O6 octahedra and corners with four equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 1°. Both U(1)-O(1) bond lengths are 2.14 Å. All U(1)-O(3) bond lengths are 2.25 Å. Si(1) is bonded to one O(2), one O(4), and two equivalent O(3) atoms to form SiO4 tetrahedra that share corners with two equivalent U(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 29°. The Si(1)-O(2) bond length is 1.64 Å. The Si(1)-O(4) bond length is 1.66 Å. Both Si(1)-O(3) bond lengths are 1.63 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to one K(1) and two equivalent U(1) atoms. In the second O site, O(2) is bonded in a linear geometry to two equivalent Si(1) atoms. In the third O site, O(3) is bonded in a 2-coordinate geometry to one Cs(1), one K(1), one U(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to two equivalent Cs(1) and two equivalent Si(1) atoms.