K3Ni2F7 crystallizes in the tetragonal I4/mmm space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 9-coordinate geometry to four equivalent F(2) and five equivalent F(3) atoms. In the second K site, K(2) is bonded to four equivalent F(1) and eight equivalent F(2) atoms to form KF12 cuboctahedra that share corners with four equivalent K(2)F12 cuboctahedra, faces with four equivalent K(2)F12 cuboctahedra, and faces with eight equivalent Ni(1)F6 octahedra. Ni(1) is bonded to one F(1), one F(3), and four equivalent F(2) atoms to form NiF6 octahedra that share corners with five equivalent Ni(1)F6 octahedra and faces with four equivalent K(2)F12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-1°. There are three inequivalent F sites. In the first F site, F(1) is bonded to four equivalent K(2) and two equivalent Ni(1) atoms to form distorted FK4Ni2 octahedra that share corners with two equivalent F(3)K5Ni octahedra, corners with four equivalent F(1)K4Ni2 octahedra, corners with sixteen equivalent F(2)K4Ni2 octahedra, edges with four equivalent F(1)K4Ni2 octahedra, and faces with eight equivalent F(2)K4Ni2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°. In the second F site, F(2) is bonded to two equivalent K(1), two equivalent K(2), and two equivalent Ni(1) atoms to form distorted FK4Ni2 octahedra that share corners with four equivalent F(1)K4Ni2 octahedra, corners with six equivalent F(3)K5Ni octahedra, corners with eight equivalent F(2)K4Ni2 octahedra, edges with three equivalent F(2)K4Ni2 octahedra, faces with two equivalent F(1)K4Ni2 octahedra, faces with two equivalent F(3)K5Ni octahedra, and faces with four equivalent F(2)K4Ni2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°. In the third F site, F(3) is bonded to five equivalent K(1) and one Ni(1) atom to form distorted FK5Ni octahedra that share  a cornercorner with one F(1)K4Ni2 octahedra, corners with four equivalent F(3)K5Ni octahedra, corners with twelve equivalent F(2)K4Ni2 octahedra, edges with eight equivalent F(3)K5Ni octahedra, and faces with four equivalent F(2)K4Ni2 octahedra. The corner-sharing octahedral tilt angles range from 0-57°.
K3Ni2F7 crystallizes in the tetragonal I4/mmm space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 9-coordinate geometry to four equivalent F(2) and five equivalent F(3) atoms. All K(1)-F(2) bond lengths are 2.76 Å. There is one shorter (2.62 Å) and four longer (2.83 Å) K(1)-F(3) bond lengths. In the second K site, K(2) is bonded to four equivalent F(1) and eight equivalent F(2) atoms to form KF12 cuboctahedra that share corners with four equivalent K(2)F12 cuboctahedra, faces with four equivalent K(2)F12 cuboctahedra, and faces with eight equivalent Ni(1)F6 octahedra. All K(2)-F(1) bond lengths are 2.83 Å. All K(2)-F(2) bond lengths are 2.82 Å. Ni(1) is bonded to one F(1), one F(3), and four equivalent F(2) atoms to form NiF6 octahedra that share corners with five equivalent Ni(1)F6 octahedra and faces with four equivalent K(2)F12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-1°. The Ni(1)-F(1) bond length is 2.01 Å. The Ni(1)-F(3) bond length is 2.00 Å. All Ni(1)-F(2) bond lengths are 2.00 Å. There are three inequivalent F sites. In the first F site, F(1) is bonded to four equivalent K(2) and two equivalent Ni(1) atoms to form distorted FK4Ni2 octahedra that share corners with two equivalent F(3)K5Ni octahedra, corners with four equivalent F(1)K4Ni2 octahedra, corners with sixteen equivalent F(2)K4Ni2 octahedra, edges with four equivalent F(1)K4Ni2 octahedra, and faces with eight equivalent F(2)K4Ni2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°. In the second F site, F(2) is bonded to two equivalent K(1), two equivalent K(2), and two equivalent Ni(1) atoms to form distorted FK4Ni2 octahedra that share corners with four equivalent F(1)K4Ni2 octahedra, corners with six equivalent F(3)K5Ni octahedra, corners with eight equivalent F(2)K4Ni2 octahedra, edges with three equivalent F(2)K4Ni2 octahedra, faces with two equivalent F(1)K4Ni2 octahedra, faces with two equivalent F(3)K5Ni octahedra, and faces with four equivalent F(2)K4Ni2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°. In the third F site, F(3) is bonded to five equivalent K(1) and one Ni(1) atom to form distorted FK5Ni octahedra that share  a cornercorner with one F(1)K4Ni2 octahedra, corners with four equivalent F(3)K5Ni octahedra, corners with twelve equivalent F(2)K4Ni2 octahedra, edges with eight equivalent F(3)K5Ni octahedra, and faces with four equivalent F(2)K4Ni2 octahedra. The corner-sharing octahedral tilt angles range from 0-57°.