Li2NiP2O7 crystallizes in the triclinic P1 space group. There are eight inequivalent Li sites. In the first Li site, Li(1) is bonded in a 4-coordinate geometry to one O(15), one O(18), one O(21), and one O(9) atom. In the second Li site, Li(2) is bonded in a 4-coordinate geometry to one O(10), one O(16), one O(17), and one O(22) atom. In the third Li site, Li(3) is bonded in a 4-coordinate geometry to one O(12), one O(13), one O(19), and one O(23) atom. In the fourth Li site, Li(4) is bonded in a 4-coordinate geometry to one O(11), one O(14), one O(20), and one O(24) atom. In the fifth Li site, Li(5) is bonded in a 4-coordinate geometry to one O(13), one O(19), one O(25), and one O(6) atom. In the sixth Li site, Li(6) is bonded in a 4-coordinate geometry to one O(14), one O(20), one O(26), and one O(5) atom. In the seventh Li site, Li(7) is bonded in a 4-coordinate geometry to one O(16), one O(17), one O(27), and one O(7) atom. In the eighth Li site, Li(8) is bonded in a 4-coordinate geometry to one O(15), one O(18), one O(28), and one O(8) atom. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(10), one O(16), one O(18), one O(22), one O(28), and one O(8) atom to form NiO6 octahedra that share  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(7)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and corners with two equivalent P(8)O4 tetrahedra. In the second Ni site, Ni(2) is bonded to one O(11), one O(14), one O(19), one O(24), one O(25), and one O(6) atom to form NiO6 octahedra that share  a cornercorner with one P(3)O4 tetrahedra,  a cornercorner with one P(6)O4 tetrahedra, corners with two equivalent P(4)O4 tetrahedra, and corners with two equivalent P(5)O4 tetrahedra. In the third Ni site, Ni(3) is bonded to one O(15), one O(17), one O(21), one O(27), one O(7), and one O(9) atom to form NiO6 octahedra that share  a cornercorner with one P(2)O4 tetrahedra,  a cornercorner with one P(8)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, and corners with two equivalent P(7)O4 tetrahedra. In the fourth Ni site, Ni(4) is bonded to one O(12), one O(13), one O(20), one O(23), one O(26), and one O(5) atom to form NiO6 octahedra that share  a cornercorner with one P(4)O4 tetrahedra,  a cornercorner with one P(5)O4 tetrahedra, corners with two equivalent P(3)O4 tetrahedra, and corners with two equivalent P(6)O4 tetrahedra. There are eight inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(15), one O(28), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra, corners with two equivalent Ni(3)O6 octahedra, and  a cornercorner with one P(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-55°. In the second P site, P(2) is bonded to one O(16), one O(2), one O(27), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(3)O6 octahedra, corners with two equivalent Ni(1)O6 octahedra, and  a cornercorner with one P(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-55°. In the third P site, P(3) is bonded to one O(1), one O(13), one O(25), and one O(5) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(2)O6 octahedra, corners with two equivalent Ni(4)O6 octahedra, and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-54°. In the fourth P site, P(4) is bonded to one O(14), one O(2), one O(26), and one O(6) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(4)O6 octahedra, corners with two equivalent Ni(2)O6 octahedra, and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-54°. In the fifth P site, P(5) is bonded to one O(11), one O(19), one O(23), and one O(3) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(4)O6 octahedra, corners with two equivalent Ni(2)O6 octahedra, and  a cornercorner with one P(7)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-55°. In the sixth P site, P(6) is bonded to one O(12), one O(20), one O(24), and one O(4) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(2)O6 octahedra, corners with two equivalent Ni(4)O6 octahedra, and  a cornercorner with one P(8)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-55°. In the seventh P site, P(7) is bonded to one O(17), one O(22), one O(3), and one O(9) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra, corners with two equivalent Ni(3)O6 octahedra, and  a cornercorner with one P(5)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-55°. In the eighth P site, P(8) is bonded to one O(10), one O(18), one O(21), and one O(4) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(3)O6 octahedra, corners with two equivalent Ni(1)O6 octahedra, and  a cornercorner with one P(6)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-55°. There are twenty-eight inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one P(1) and one P(3) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one P(2) and one P(4) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one P(5) and one P(7) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one P(6) and one P(8) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Li(6), one Ni(4), and one P(3) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Li(5), one Ni(2), and one P(4) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Li(7), one Ni(3), and one P(1) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Li(8), one Ni(1), and one P(2) atom. In the ninth O site, O(9) is bonded in a distorted trigonal planar geometry to one Li(1), one Ni(3), and one P(7) atom. In the tenth O site, O(10) is bonded in a distorted trigonal planar geometry to one Li(2), one Ni(1), and one P(8) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal planar geometry to one Li(4), one Ni(2), and one P(5) atom. In the twelfth O site, O(12) is bonded in a distorted trigonal planar geometry to one Li(3), one Ni(4), and one P(6) atom. In the thirteenth O site, O(13) is bonded to one Li(3), one Li(5), one Ni(4), and one P(3) atom to form a mixture of distorted corner and edge-sharing OLi2NiP trigonal pyramids. In the fourteenth O site, O(14) is bonded to one Li(4), one Li(6), one Ni(2), and one P(4) atom to form a mixture of distorted corner and edge-sharing OLi2NiP trigonal pyramids. In the fifteenth O site, O(15) is bonded to one Li(1), one Li(8), one Ni(3), and one P(1) atom to form a mixture of distorted corner and edge-sharing OLi2NiP tetrahedra. In the sixteenth O site, O(16) is bonded to one Li(2), one Li(7), one Ni(1), and one P(2) atom to form a mixture of distorted corner and edge-sharing OLi2NiP tetrahedra. In the seventeenth O site, O(17) is bonded to one Li(2), one Li(7), one Ni(3), and one P(7) atom to form a mixture of distorted corner and edge-sharing OLi2NiP tetrahedra. In the eighteenth O site, O(18) is bonded to one Li(1), one Li(8), one Ni(1), and one P(8) atom to form a mixture of distorted corner and edge-sharing OLi2NiP tetrahedra. In the nineteenth O site, O(19) is bonded to one Li(3), one Li(5), one Ni(2), and one P(5) atom to form a mixture of distorted corner and edge-sharing OLi2NiP tetrahedra. In the twentieth O site, O(20) is bonded to one Li(4), one Li(6), one Ni(4), and one P(6) atom to form a mixture of distorted corner and edge-sharing OLi2NiP trigonal pyramids. In the twenty-first O site, O(21) is bonded in a distorted trigonal planar geometry to one Li(1), one Ni(3), and one P(8) atom. In the twenty-second O site, O(22) is bonded in a distorted trigonal planar geometry to one Li(2), one Ni(1), and one P(7) atom. In the twenty-third O site, O(23) is bonded in a distorted trigonal planar geometry to one Li(3), one Ni(4), and one P(5) atom. In the twenty-fourth O site, O(24) is bonded in a distorted trigonal planar geometry to one Li(4), one Ni(2), and one P(6) atom. In the twenty-fifth O site, O(25) is bonded in a distorted trigonal planar geometry to one Li(5), one Ni(2), and one P(3) atom. In the twenty-sixth O site, O(26) is bonded in a distorted trigonal planar geometry to one Li(6), one Ni(4), and one P(4) atom. In the twenty-seventh O site, O(27) is bonded in a distorted trigonal planar geometry to one Li(7), one Ni(3), and one P(2) atom. In the twenty-eighth O site, O(28) is bonded in a distorted trigonal planar geometry to one Li(8), one Ni(1), and one P(1) atom.
Li2NiP2O7 crystallizes in the triclinic P1 space group. There are eight inequivalent Li sites. In the first Li site, Li(1) is bonded in a 4-coordinate geometry to one O(15), one O(18), one O(21), and one O(9) atom. The Li(1)-O(15) bond length is 2.26 Å. The Li(1)-O(18) bond length is 1.99 Å. The Li(1)-O(21) bond length is 1.94 Å. The Li(1)-O(9) bond length is 1.97 Å. In the second Li site, Li(2) is bonded in a 4-coordinate geometry to one O(10), one O(16), one O(17), and one O(22) atom. The Li(2)-O(10) bond length is 1.97 Å. The Li(2)-O(16) bond length is 2.26 Å. The Li(2)-O(17) bond length is 1.99 Å. The Li(2)-O(22) bond length is 1.94 Å. In the third Li site, Li(3) is bonded in a 4-coordinate geometry to one O(12), one O(13), one O(19), and one O(23) atom. The Li(3)-O(12) bond length is 1.96 Å. The Li(3)-O(13) bond length is 2.28 Å. The Li(3)-O(19) bond length is 1.99 Å. The Li(3)-O(23) bond length is 1.94 Å. In the fourth Li site, Li(4) is bonded in a 4-coordinate geometry to one O(11), one O(14), one O(20), and one O(24) atom. The Li(4)-O(11) bond length is 1.96 Å. The Li(4)-O(14) bond length is 2.28 Å. The Li(4)-O(20) bond length is 1.99 Å. The Li(4)-O(24) bond length is 1.94 Å. In the fifth Li site, Li(5) is bonded in a 4-coordinate geometry to one O(13), one O(19), one O(25), and one O(6) atom. The Li(5)-O(13) bond length is 1.99 Å. The Li(5)-O(19) bond length is 2.28 Å. The Li(5)-O(25) bond length is 1.94 Å. The Li(5)-O(6) bond length is 1.97 Å. In the sixth Li site, Li(6) is bonded in a 4-coordinate geometry to one O(14), one O(20), one O(26), and one O(5) atom. The Li(6)-O(14) bond length is 1.99 Å. The Li(6)-O(20) bond length is 2.28 Å. The Li(6)-O(26) bond length is 1.94 Å. The Li(6)-O(5) bond length is 1.96 Å. In the seventh Li site, Li(7) is bonded in a 4-coordinate geometry to one O(16), one O(17), one O(27), and one O(7) atom. The Li(7)-O(16) bond length is 2.00 Å. The Li(7)-O(17) bond length is 2.26 Å. The Li(7)-O(27) bond length is 1.94 Å. The Li(7)-O(7) bond length is 1.97 Å. In the eighth Li site, Li(8) is bonded in a 4-coordinate geometry to one O(15), one O(18), one O(28), and one O(8) atom. The Li(8)-O(15) bond length is 2.00 Å. The Li(8)-O(18) bond length is 2.26 Å. The Li(8)-O(28) bond length is 1.94 Å. The Li(8)-O(8) bond length is 1.96 Å. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(10), one O(16), one O(18), one O(22), one O(28), and one O(8) atom to form NiO6 octahedra that share  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(7)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and corners with two equivalent P(8)O4 tetrahedra. The Ni(1)-O(10) bond length is 2.07 Å. The Ni(1)-O(16) bond length is 2.09 Å. The Ni(1)-O(18) bond length is 2.08 Å. The Ni(1)-O(22) bond length is 2.21 Å. The Ni(1)-O(28) bond length is 2.22 Å. The Ni(1)-O(8) bond length is 2.06 Å. In the second Ni site, Ni(2) is bonded to one O(11), one O(14), one O(19), one O(24), one O(25), and one O(6) atom to form NiO6 octahedra that share  a cornercorner with one P(3)O4 tetrahedra,  a cornercorner with one P(6)O4 tetrahedra, corners with two equivalent P(4)O4 tetrahedra, and corners with two equivalent P(5)O4 tetrahedra. The Ni(2)-O(11) bond length is 2.07 Å. The Ni(2)-O(14) bond length is 2.08 Å. The Ni(2)-O(19) bond length is 2.08 Å. The Ni(2)-O(24) bond length is 2.21 Å. The Ni(2)-O(25) bond length is 2.21 Å. The Ni(2)-O(6) bond length is 2.07 Å. In the third Ni site, Ni(3) is bonded to one O(15), one O(17), one O(21), one O(27), one O(7), and one O(9) atom to form NiO6 octahedra that share  a cornercorner with one P(2)O4 tetrahedra,  a cornercorner with one P(8)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, and corners with two equivalent P(7)O4 tetrahedra. The Ni(3)-O(15) bond length is 2.08 Å. The Ni(3)-O(17) bond length is 2.09 Å. The Ni(3)-O(21) bond length is 2.21 Å. The Ni(3)-O(27) bond length is 2.21 Å. The Ni(3)-O(7) bond length is 2.06 Å. The Ni(3)-O(9) bond length is 2.07 Å. In the fourth Ni site, Ni(4) is bonded to one O(12), one O(13), one O(20), one O(23), one O(26), and one O(5) atom to form NiO6 octahedra that share  a cornercorner with one P(4)O4 tetrahedra,  a cornercorner with one P(5)O4 tetrahedra, corners with two equivalent P(3)O4 tetrahedra, and corners with two equivalent P(6)O4 tetrahedra. The Ni(4)-O(12) bond length is 2.07 Å. The Ni(4)-O(13) bond length is 2.08 Å. The Ni(4)-O(20) bond length is 2.08 Å. The Ni(4)-O(23) bond length is 2.21 Å. The Ni(4)-O(26) bond length is 2.21 Å. The Ni(4)-O(5) bond length is 2.06 Å. There are eight inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(15), one O(28), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra, corners with two equivalent Ni(3)O6 octahedra, and  a cornercorner with one P(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-55°. The P(1)-O(1) bond length is 1.61 Å. The P(1)-O(15) bond length is 1.53 Å. The P(1)-O(28) bond length is 1.54 Å. The P(1)-O(7) bond length is 1.53 Å. In the second P site, P(2) is bonded to one O(16), one O(2), one O(27), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(3)O6 octahedra, corners with two equivalent Ni(1)O6 octahedra, and  a cornercorner with one P(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-55°. The P(2)-O(16) bond length is 1.53 Å. The P(2)-O(2) bond length is 1.61 Å. The P(2)-O(27) bond length is 1.54 Å. The P(2)-O(8) bond length is 1.53 Å. In the third P site, P(3) is bonded to one O(1), one O(13), one O(25), and one O(5) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(2)O6 octahedra, corners with two equivalent Ni(4)O6 octahedra, and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-54°. The P(3)-O(1) bond length is 1.61 Å. The P(3)-O(13) bond length is 1.53 Å. The P(3)-O(25) bond length is 1.53 Å. The P(3)-O(5) bond length is 1.53 Å. In the fourth P site, P(4) is bonded to one O(14), one O(2), one O(26), and one O(6) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(4)O6 octahedra, corners with two equivalent Ni(2)O6 octahedra, and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-54°. The P(4)-O(14) bond length is 1.53 Å. The P(4)-O(2) bond length is 1.61 Å. The P(4)-O(26) bond length is 1.54 Å. The P(4)-O(6) bond length is 1.53 Å. In the fifth P site, P(5) is bonded to one O(11), one O(19), one O(23), and one O(3) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(4)O6 octahedra, corners with two equivalent Ni(2)O6 octahedra, and  a cornercorner with one P(7)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-55°. The P(5)-O(11) bond length is 1.53 Å. The P(5)-O(19) bond length is 1.53 Å. The P(5)-O(23) bond length is 1.53 Å. The P(5)-O(3) bond length is 1.61 Å. In the sixth P site, P(6) is bonded to one O(12), one O(20), one O(24), and one O(4) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(2)O6 octahedra, corners with two equivalent Ni(4)O6 octahedra, and  a cornercorner with one P(8)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-55°. The P(6)-O(12) bond length is 1.53 Å. The P(6)-O(20) bond length is 1.53 Å. The P(6)-O(24) bond length is 1.53 Å. The P(6)-O(4) bond length is 1.61 Å. In the seventh P site, P(7) is bonded to one O(17), one O(22), one O(3), and one O(9) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra, corners with two equivalent Ni(3)O6 octahedra, and  a cornercorner with one P(5)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-55°. The P(7)-O(17) bond length is 1.53 Å. The P(7)-O(22) bond length is 1.53 Å. The P(7)-O(3) bond length is 1.61 Å. The P(7)-O(9) bond length is 1.53 Å. In the eighth P site, P(8) is bonded to one O(10), one O(18), one O(21), and one O(4) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(3)O6 octahedra, corners with two equivalent Ni(1)O6 octahedra, and  a cornercorner with one P(6)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-55°. The P(8)-O(10) bond length is 1.53 Å. The P(8)-O(18) bond length is 1.53 Å. The P(8)-O(21) bond length is 1.54 Å. The P(8)-O(4) bond length is 1.61 Å. There are twenty-eight inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one P(1) and one P(3) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one P(2) and one P(4) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one P(5) and one P(7) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one P(6) and one P(8) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Li(6), one Ni(4), and one P(3) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Li(5), one Ni(2), and one P(4) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Li(7), one Ni(3), and one P(1) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Li(8), one Ni(1), and one P(2) atom. In the ninth O site, O(9) is bonded in a distorted trigonal planar geometry to one Li(1), one Ni(3), and one P(7) atom. In the tenth O site, O(10) is bonded in a distorted trigonal planar geometry to one Li(2), one Ni(1), and one P(8) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal planar geometry to one Li(4), one Ni(2), and one P(5) atom. In the twelfth O site, O(12) is bonded in a distorted trigonal planar geometry to one Li(3), one Ni(4), and one P(6) atom. In the thirteenth O site, O(13) is bonded to one Li(3), one Li(5), one Ni(4), and one P(3) atom to form a mixture of distorted corner and edge-sharing OLi2NiP trigonal pyramids. In the fourteenth O site, O(14) is bonded to one Li(4), one Li(6), one Ni(2), and one P(4) atom to form a mixture of distorted corner and edge-sharing OLi2NiP trigonal pyramids. In the fifteenth O site, O(15) is bonded to one Li(1), one Li(8), one Ni(3), and one P(1) atom to form a mixture of distorted corner and edge-sharing OLi2NiP tetrahedra. In the sixteenth O site, O(16) is bonded to one Li(2), one Li(7), one Ni(1), and one P(2) atom to form a mixture of distorted corner and edge-sharing OLi2NiP tetrahedra. In the seventeenth O site, O(17) is bonded to one Li(2), one Li(7), one Ni(3), and one P(7) atom to form a mixture of distorted corner and edge-sharing OLi2NiP tetrahedra. In the eighteenth O site, O(18) is bonded to one Li(1), one Li(8), one Ni(1), and one P(8) atom to form a mixture of distorted corner and edge-sharing OLi2NiP tetrahedra. In the nineteenth O site, O(19) is bonded to one Li(3), one Li(5), one Ni(2), and one P(5) atom to form a mixture of distorted corner and edge-sharing OLi2NiP tetrahedra. In the twentieth O site, O(20) is bonded to one Li(4), one Li(6), one Ni(4), and one P(6) atom to form a mixture of distorted corner and edge-sharing OLi2NiP trigonal pyramids. In the twenty-first O site, O(21) is bonded in a distorted trigonal planar geometry to one Li(1), one Ni(3), and one P(8) atom. In the twenty-second O site, O(22) is bonded in a distorted trigonal planar geometry to one Li(2), one Ni(1), and one P(7) atom. In the twenty-third O site, O(23) is bonded in a distorted trigonal planar geometry to one Li(3), one Ni(4), and one P(5) atom. In the twenty-fourth O site, O(24) is bonded in a distorted trigonal planar geometry to one Li(4), one Ni(2), and one P(6) atom. In the twenty-fifth O site, O(25) is bonded in a distorted trigonal planar geometry to one Li(5), one Ni(2), and one P(3) atom. In the twenty-sixth O site, O(26) is bonded in a distorted trigonal planar geometry to one Li(6), one Ni(4), and one P(4) atom. In the twenty-seventh O site, O(27) is bonded in a distorted trigonal planar geometry to one Li(7), one Ni(3), and one P(2) atom. In the twenty-eighth O site, O(28) is bonded in a distorted trigonal planar geometry to one Li(8), one Ni(1), and one P(1) atom.