RbCr4O8 crystallizes in the triclinic P1 space group. Rb(1) is bonded in a distorted body-centered cubic geometry to two equivalent O(5), two equivalent O(6), two equivalent O(7), and two equivalent O(8) atoms. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(4), one O(6), two equivalent O(2), and two equivalent O(8) atoms to form a mixture of corner and edge-sharing CrO6 octahedra. The corner-sharing octahedral tilt angles range from 49-53°. In the second Cr site, Cr(2) is bonded to one O(1), one O(5), two equivalent O(4), and two equivalent O(7) atoms to form a mixture of corner and edge-sharing CrO6 octahedra. The corner-sharing octahedral tilt angles range from 49-52°. In the third Cr site, Cr(3) is bonded to one O(3), one O(8), two equivalent O(1), and two equivalent O(6) atoms to form a mixture of corner and edge-sharing CrO6 octahedra. The corner-sharing octahedral tilt angles range from 50-51°. In the fourth Cr site, Cr(4) is bonded to one O(2), one O(7), two equivalent O(3), and two equivalent O(5) atoms to form a mixture of corner and edge-sharing CrO6 octahedra. The corner-sharing octahedral tilt angles range from 50-53°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Cr(2) and two equivalent Cr(3) atoms. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Cr(4) and two equivalent Cr(1) atoms. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Cr(3) and two equivalent Cr(4) atoms. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Cr(1) and two equivalent Cr(2) atoms. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to two equivalent Rb(1), one Cr(2), and two equivalent Cr(4) atoms. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to two equivalent Rb(1), one Cr(1), and two equivalent Cr(3) atoms. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to two equivalent Rb(1), one Cr(4), and two equivalent Cr(2) atoms. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to two equivalent Rb(1), one Cr(3), and two equivalent Cr(1) atoms.
RbCr4O8 crystallizes in the triclinic P1 space group. Rb(1) is bonded in a distorted body-centered cubic geometry to two equivalent O(5), two equivalent O(6), two equivalent O(7), and two equivalent O(8) atoms. There is one shorter (2.97 Å) and one longer (3.01 Å) Rb(1)-O(5) bond length. Both Rb(1)-O(6) bond lengths are 3.01 Å. There is one shorter (2.96 Å) and one longer (2.98 Å) Rb(1)-O(7) bond length. There is one shorter (2.98 Å) and one longer (3.01 Å) Rb(1)-O(8) bond length. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(4), one O(6), two equivalent O(2), and two equivalent O(8) atoms to form a mixture of corner and edge-sharing CrO6 octahedra. The corner-sharing octahedral tilt angles range from 49-53°. The Cr(1)-O(4) bond length is 1.92 Å. The Cr(1)-O(6) bond length is 1.95 Å. There is one shorter (1.89 Å) and one longer (2.01 Å) Cr(1)-O(2) bond length. There is one shorter (2.00 Å) and one longer (2.02 Å) Cr(1)-O(8) bond length. In the second Cr site, Cr(2) is bonded to one O(1), one O(5), two equivalent O(4), and two equivalent O(7) atoms to form a mixture of corner and edge-sharing CrO6 octahedra. The corner-sharing octahedral tilt angles range from 49-52°. The Cr(2)-O(1) bond length is 1.90 Å. The Cr(2)-O(5) bond length is 1.94 Å. There is one shorter (1.94 Å) and one longer (1.98 Å) Cr(2)-O(4) bond length. There is one shorter (2.00 Å) and one longer (2.01 Å) Cr(2)-O(7) bond length. In the third Cr site, Cr(3) is bonded to one O(3), one O(8), two equivalent O(1), and two equivalent O(6) atoms to form a mixture of corner and edge-sharing CrO6 octahedra. The corner-sharing octahedral tilt angles range from 50-51°. The Cr(3)-O(3) bond length is 1.89 Å. The Cr(3)-O(8) bond length is 1.96 Å. Both Cr(3)-O(1) bond lengths are 1.97 Å. There is one shorter (2.00 Å) and one longer (2.01 Å) Cr(3)-O(6) bond length. In the fourth Cr site, Cr(4) is bonded to one O(2), one O(7), two equivalent O(3), and two equivalent O(5) atoms to form a mixture of corner and edge-sharing CrO6 octahedra. The corner-sharing octahedral tilt angles range from 50-53°. The Cr(4)-O(2) bond length is 1.96 Å. The Cr(4)-O(7) bond length is 1.98 Å. Both Cr(4)-O(3) bond lengths are 1.97 Å. There is one shorter (2.00 Å) and one longer (2.01 Å) Cr(4)-O(5) bond length. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Cr(2) and two equivalent Cr(3) atoms. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Cr(4) and two equivalent Cr(1) atoms. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Cr(3) and two equivalent Cr(4) atoms. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Cr(1) and two equivalent Cr(2) atoms. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to two equivalent Rb(1), one Cr(2), and two equivalent Cr(4) atoms. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to two equivalent Rb(1), one Cr(1), and two equivalent Cr(3) atoms. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to two equivalent Rb(1), one Cr(4), and two equivalent Cr(2) atoms. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to two equivalent Rb(1), one Cr(3), and two equivalent Cr(1) atoms.