KNaMg2Si4(O5F)2 crystallizes in the monoclinic C2/m space group. K(1) is bonded to four equivalent O(2) and eight equivalent O(3) atoms to form KO12 cuboctahedra that share edges with six equivalent K(1)O12 cuboctahedra and edges with twelve equivalent Si(1)O4 tetrahedra. Na(1) is bonded to four equivalent O(1) and two equivalent F(1) atoms to form NaO4F2 octahedra that share corners with four equivalent Si(1)O4 tetrahedra and edges with six equivalent Mg(1)O4F2 octahedra. Mg(1) is bonded to four equivalent O(1) and two equivalent F(1) atoms to form MgO4F2 octahedra that share corners with four equivalent Si(1)O4 tetrahedra, edges with three equivalent Na(1)O4F2 octahedra, and edges with three equivalent Mg(1)O4F2 octahedra. Si(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form SiO4 tetrahedra that share  a cornercorner with one Na(1)O4F2 octahedra, corners with two equivalent Mg(1)O4F2 octahedra, corners with three equivalent Si(1)O4 tetrahedra, and edges with three equivalent K(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 52-62°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Na(1), two equivalent Mg(1), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent K(1) and two equivalent Si(1) atoms. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to two equivalent K(1) and two equivalent Si(1) atoms. F(1) is bonded in a distorted T-shaped geometry to one Na(1) and two equivalent Mg(1) atoms.
KNaMg2Si4(O5F)2 crystallizes in the monoclinic C2/m space group. K(1) is bonded to four equivalent O(2) and eight equivalent O(3) atoms to form KO12 cuboctahedra that share edges with six equivalent K(1)O12 cuboctahedra and edges with twelve equivalent Si(1)O4 tetrahedra. There are two shorter (3.13 Å) and two longer (3.26 Å) K(1)-O(2) bond lengths. There are four shorter (3.12 Å) and four longer (3.13 Å) K(1)-O(3) bond lengths. Na(1) is bonded to four equivalent O(1) and two equivalent F(1) atoms to form NaO4F2 octahedra that share corners with four equivalent Si(1)O4 tetrahedra and edges with six equivalent Mg(1)O4F2 octahedra. All Na(1)-O(1) bond lengths are 2.28 Å. Both Na(1)-F(1) bond lengths are 2.24 Å. Mg(1) is bonded to four equivalent O(1) and two equivalent F(1) atoms to form MgO4F2 octahedra that share corners with four equivalent Si(1)O4 tetrahedra, edges with three equivalent Na(1)O4F2 octahedra, and edges with three equivalent Mg(1)O4F2 octahedra. There are two shorter (2.07 Å) and two longer (2.09 Å) Mg(1)-O(1) bond lengths. Both Mg(1)-F(1) bond lengths are 2.01 Å. Si(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form SiO4 tetrahedra that share  a cornercorner with one Na(1)O4F2 octahedra, corners with two equivalent Mg(1)O4F2 octahedra, corners with three equivalent Si(1)O4 tetrahedra, and edges with three equivalent K(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 52-62°. The Si(1)-O(1) bond length is 1.60 Å. The Si(1)-O(2) bond length is 1.66 Å. Both Si(1)-O(3) bond lengths are 1.67 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Na(1), two equivalent Mg(1), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent K(1) and two equivalent Si(1) atoms. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to two equivalent K(1) and two equivalent Si(1) atoms. F(1) is bonded in a distorted T-shaped geometry to one Na(1) and two equivalent Mg(1) atoms.