K2B4O7 crystallizes in the triclinic P-1 space group. There are four inequivalent K sites. In the first K site, K(1) is bonded in a 8-coordinate geometry to one O(11), one O(2), one O(3), one O(6), two equivalent O(5), and two equivalent O(9) atoms. In the second K site, K(2) is bonded in a 8-coordinate geometry to one O(11), one O(2), one O(3), one O(9), two equivalent O(10), and two equivalent O(4) atoms. In the third K site, K(3) is bonded in a 6-coordinate geometry to one O(1), one O(12), one O(4), one O(7), and two equivalent O(8) atoms. In the fourth K site, K(4) is bonded in a 6-coordinate geometry to one O(1), one O(14), one O(6), one O(7), and two equivalent O(13) atoms. There are eight inequivalent B sites. In the first B site, B(1) is bonded in a trigonal planar geometry to one O(10), one O(3), and one O(9) atom. In the second B site, B(2) is bonded in a trigonal planar geometry to one O(11), one O(14), and one O(6) atom. In the third B site, B(3) is bonded in a trigonal planar geometry to one O(12), one O(4), and one O(8) atom. In the fourth B site, B(4) is bonded in a trigonal planar geometry to one O(13), one O(2), and one O(5) atom. In the fifth B site, B(5) is bonded to one O(5), one O(6), one O(7), and one O(9) atom to form corner-sharing BO4 tetrahedra. In the sixth B site, B(6) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form corner-sharing BO4 tetrahedra. In the seventh B site, B(7) is bonded to one O(1), one O(12), one O(13), and one O(14) atom to form corner-sharing BO4 tetrahedra. In the eighth B site, B(8) is bonded to one O(10), one O(11), one O(7), and one O(8) atom to form corner-sharing BO4 tetrahedra. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted water-like geometry to one K(3), one K(4), one B(6), and one B(7) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one K(1), one K(2), one B(4), and one B(6) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one K(1), one K(2), one B(1), and one B(6) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one K(3), two equivalent K(2), one B(3), and one B(6) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to two equivalent K(1), one B(4), and one B(5) atom. In the sixth O site, O(6) is bonded in a distorted bent 150 degrees geometry to one K(1), one K(4), one B(2), and one B(5) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one K(3), one K(4), one B(5), and one B(8) atom. In the eighth O site, O(8) is bonded in a distorted bent 120 degrees geometry to two equivalent K(3), one B(3), and one B(8) atom. In the ninth O site, O(9) is bonded in a distorted bent 120 degrees geometry to one K(2), two equivalent K(1), one B(1), and one B(5) atom. In the tenth O site, O(10) is bonded in a distorted bent 120 degrees geometry to two equivalent K(2), one B(1), and one B(8) atom. In the eleventh O site, O(11) is bonded in a distorted bent 120 degrees geometry to one K(1), one K(2), one B(2), and one B(8) atom. In the twelfth O site, O(12) is bonded in a distorted bent 120 degrees geometry to one K(3), one B(3), and one B(7) atom. In the thirteenth O site, O(13) is bonded in a distorted bent 120 degrees geometry to two equivalent K(4), one B(4), and one B(7) atom. In the fourteenth O site, O(14) is bonded in a 2-coordinate geometry to one K(4), one B(2), and one B(7) atom.
K2B4O7 crystallizes in the triclinic P-1 space group. There are four inequivalent K sites. In the first K site, K(1) is bonded in a 8-coordinate geometry to one O(11), one O(2), one O(3), one O(6), two equivalent O(5), and two equivalent O(9) atoms. The K(1)-O(11) bond length is 2.72 Å. The K(1)-O(2) bond length is 2.80 Å. The K(1)-O(3) bond length is 3.01 Å. The K(1)-O(6) bond length is 2.88 Å. There is one shorter (2.75 Å) and one longer (3.08 Å) K(1)-O(5) bond length. There is one shorter (2.96 Å) and one longer (3.04 Å) K(1)-O(9) bond length. In the second K site, K(2) is bonded in a 8-coordinate geometry to one O(11), one O(2), one O(3), one O(9), two equivalent O(10), and two equivalent O(4) atoms. The K(2)-O(11) bond length is 2.92 Å. The K(2)-O(2) bond length is 2.81 Å. The K(2)-O(3) bond length is 2.92 Å. The K(2)-O(9) bond length is 2.66 Å. There is one shorter (2.72 Å) and one longer (2.84 Å) K(2)-O(10) bond length. There is one shorter (2.73 Å) and one longer (2.81 Å) K(2)-O(4) bond length. In the third K site, K(3) is bonded in a 6-coordinate geometry to one O(1), one O(12), one O(4), one O(7), and two equivalent O(8) atoms. The K(3)-O(1) bond length is 2.74 Å. The K(3)-O(12) bond length is 2.67 Å. The K(3)-O(4) bond length is 2.97 Å. The K(3)-O(7) bond length is 2.80 Å. There is one shorter (2.70 Å) and one longer (3.07 Å) K(3)-O(8) bond length. In the fourth K site, K(4) is bonded in a 6-coordinate geometry to one O(1), one O(14), one O(6), one O(7), and two equivalent O(13) atoms. The K(4)-O(1) bond length is 2.77 Å. The K(4)-O(14) bond length is 2.66 Å. The K(4)-O(6) bond length is 2.84 Å. The K(4)-O(7) bond length is 2.64 Å. There is one shorter (2.76 Å) and one longer (2.82 Å) K(4)-O(13) bond length. There are eight inequivalent B sites. In the first B site, B(1) is bonded in a trigonal planar geometry to one O(10), one O(3), and one O(9) atom. The B(1)-O(10) bond length is 1.36 Å. The B(1)-O(3) bond length is 1.38 Å. The B(1)-O(9) bond length is 1.38 Å. In the second B site, B(2) is bonded in a trigonal planar geometry to one O(11), one O(14), and one O(6) atom. The B(2)-O(11) bond length is 1.37 Å. The B(2)-O(14) bond length is 1.36 Å. The B(2)-O(6) bond length is 1.37 Å. In the third B site, B(3) is bonded in a trigonal planar geometry to one O(12), one O(4), and one O(8) atom. The B(3)-O(12) bond length is 1.37 Å. The B(3)-O(4) bond length is 1.38 Å. The B(3)-O(8) bond length is 1.36 Å. In the fourth B site, B(4) is bonded in a trigonal planar geometry to one O(13), one O(2), and one O(5) atom. The B(4)-O(13) bond length is 1.37 Å. The B(4)-O(2) bond length is 1.38 Å. The B(4)-O(5) bond length is 1.36 Å. In the fifth B site, B(5) is bonded to one O(5), one O(6), one O(7), and one O(9) atom to form corner-sharing BO4 tetrahedra. The B(5)-O(5) bond length is 1.50 Å. The B(5)-O(6) bond length is 1.47 Å. The B(5)-O(7) bond length is 1.43 Å. The B(5)-O(9) bond length is 1.50 Å. In the sixth B site, B(6) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form corner-sharing BO4 tetrahedra. The B(6)-O(1) bond length is 1.44 Å. The B(6)-O(2) bond length is 1.51 Å. The B(6)-O(3) bond length is 1.47 Å. The B(6)-O(4) bond length is 1.50 Å. In the seventh B site, B(7) is bonded to one O(1), one O(12), one O(13), and one O(14) atom to form corner-sharing BO4 tetrahedra. The B(7)-O(1) bond length is 1.46 Å. The B(7)-O(12) bond length is 1.50 Å. The B(7)-O(13) bond length is 1.50 Å. The B(7)-O(14) bond length is 1.44 Å. In the eighth B site, B(8) is bonded to one O(10), one O(11), one O(7), and one O(8) atom to form corner-sharing BO4 tetrahedra. The B(8)-O(10) bond length is 1.50 Å. The B(8)-O(11) bond length is 1.49 Å. The B(8)-O(7) bond length is 1.44 Å. The B(8)-O(8) bond length is 1.49 Å. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted water-like geometry to one K(3), one K(4), one B(6), and one B(7) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one K(1), one K(2), one B(4), and one B(6) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one K(1), one K(2), one B(1), and one B(6) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one K(3), two equivalent K(2), one B(3), and one B(6) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to two equivalent K(1), one B(4), and one B(5) atom. In the sixth O site, O(6) is bonded in a distorted bent 150 degrees geometry to one K(1), one K(4), one B(2), and one B(5) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one K(3), one K(4), one B(5), and one B(8) atom. In the eighth O site, O(8) is bonded in a distorted bent 120 degrees geometry to two equivalent K(3), one B(3), and one B(8) atom. In the ninth O site, O(9) is bonded in a distorted bent 120 degrees geometry to one K(2), two equivalent K(1), one B(1), and one B(5) atom. In the tenth O site, O(10) is bonded in a distorted bent 120 degrees geometry to two equivalent K(2), one B(1), and one B(8) atom. In the eleventh O site, O(11) is bonded in a distorted bent 120 degrees geometry to one K(1), one K(2), one B(2), and one B(8) atom. In the twelfth O site, O(12) is bonded in a distorted bent 120 degrees geometry to one K(3), one B(3), and one B(7) atom. In the thirteenth O site, O(13) is bonded in a distorted bent 120 degrees geometry to two equivalent K(4), one B(4), and one B(7) atom. In the fourteenth O site, O(14) is bonded in a 2-coordinate geometry to one K(4), one B(2), and one B(7) atom.