NiP2O7 crystallizes in the triclinic P1 space group. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(12), one O(18), one O(21), one O(27), one O(5), and one O(7) atom to form NiO6 octahedra that share  a cornercorner with one Ni(3)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra,  a cornercorner with one P(5)O4 tetrahedra,  a cornercorner with one P(8)O4 tetrahedra, and corners with two equivalent P(4)O4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. In the second Ni site, Ni(2) is bonded to one O(14), one O(15), one O(16), one O(20), one O(22), and one O(8) atom to form NiO6 octahedra that share  a cornercorner with one Ni(4)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra,  a cornercorner with one P(6)O4 tetrahedra,  a cornercorner with one P(7)O4 tetrahedra, and  an edgeedge with one P(5)O4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. In the third Ni site, Ni(3) is bonded to one O(1), one O(11), one O(12), one O(17), one O(26), and one O(4) atom to form NiO6 octahedra that share  a cornercorner with one Ni(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra,  a cornercorner with one P(7)O4 tetrahedra, and  an edgeedge with one P(8)O4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. In the fourth Ni site, Ni(4) is bonded to one O(13), one O(19), one O(20), one O(25), one O(28), and one O(9) atom to form NiO6 octahedra that share  a cornercorner with one Ni(2)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra,  a cornercorner with one P(5)O4 tetrahedra,  a cornercorner with one P(7)O4 tetrahedra,  a cornercorner with one P(8)O4 tetrahedra, and corners with two equivalent P(6)O4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. There are eight inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(18), one O(23), and one O(3) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra,  a cornercorner with one Ni(3)O6 octahedra, and  a cornercorner with one P(7)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 45-53°. In the second P site, P(2) is bonded to one O(2), one O(24), one O(25), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(2)O6 octahedra,  a cornercorner with one Ni(4)O6 octahedra, and  a cornercorner with one P(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 44-54°. In the third P site, P(3) is bonded to one O(11), one O(16), one O(24), and one O(27) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra,  a cornercorner with one Ni(2)O6 octahedra,  a cornercorner with one Ni(3)O6 octahedra, and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 44-48°. In the fourth P site, P(4) is bonded to one O(10), one O(4), one O(5), and one O(7) 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(5)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 41-49°. In the fifth P site, P(5) is bonded to one O(10), one O(20), one O(21), and one O(22) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra,  a cornercorner with one Ni(4)O6 octahedra,  a cornercorner with one P(4)O4 tetrahedra, and  an edgeedge with one Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-51°. In the sixth P site, P(6) is bonded to one O(13), one O(15), one O(19), and one O(6) 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 41-49°. In the seventh P site, P(7) is bonded to one O(14), one O(17), one O(3), and one O(9) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(2)O6 octahedra,  a cornercorner with one Ni(3)O6 octahedra,  a cornercorner with one Ni(4)O6 octahedra, and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 45-48°. In the eighth P site, P(8) is bonded to one O(12), one O(26), one O(28), and one O(6) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra,  a cornercorner with one Ni(4)O6 octahedra,  a cornercorner with one P(6)O4 tetrahedra, and  an edgeedge with one Ni(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-51°. There are twenty-eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Ni(3) and one P(1) atom. In the second O site, O(2) is bonded in a single-bond geometry to one P(2) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one P(1) and one P(7) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one Ni(3) and one P(4) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Ni(1) and one P(4) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one P(6) and one P(8) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Ni(1) and one P(4) atom. In the eighth O site, O(8) is bonded in a distorted bent 150 degrees geometry to one Ni(2) and one P(2) atom. In the ninth O site, O(9) is bonded in a distorted bent 150 degrees geometry to one Ni(4) and one P(7) atom. In the tenth O site, O(10) is bonded in a bent 120 degrees geometry to one P(4) and one P(5) atom. In the eleventh O site, O(11) is bonded in a distorted bent 120 degrees geometry to one Ni(3) and one P(3) atom. In the twelfth O site, O(12) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(3), and one P(8) atom. In the thirteenth O site, O(13) is bonded in a bent 150 degrees geometry to one Ni(4) and one P(6) atom. In the fourteenth O site, O(14) is bonded in a distorted bent 120 degrees geometry to one Ni(2) and one P(7) atom. In the fifteenth O site, O(15) is bonded in a distorted bent 120 degrees geometry to one Ni(2) and one P(6) atom. In the sixteenth O site, O(16) is bonded in a bent 120 degrees geometry to one Ni(2) and one P(3) atom. In the seventeenth O site, O(17) is bonded in a bent 120 degrees geometry to one Ni(3) and one P(7) atom. In the eighteenth O site, O(18) is bonded in a bent 120 degrees geometry to one Ni(1) and one P(1) atom. In the nineteenth O site, O(19) is bonded in a bent 120 degrees geometry to one Ni(4) and one P(6) atom. In the twentieth O site, O(20) is bonded in a distorted trigonal planar geometry to one Ni(2), one Ni(4), and one P(5) atom. In the twenty-first O site, O(21) is bonded in a bent 120 degrees geometry to one Ni(1) and one P(5) atom. In the twenty-second O site, O(22) is bonded in an L-shaped geometry to one Ni(2) and one P(5) atom. In the twenty-third O site, O(23) is bonded in a single-bond geometry to one P(1) atom. In the twenty-fourth O site, O(24) is bonded in a bent 120 degrees geometry to one P(2) and one P(3) atom. In the twenty-fifth O site, O(25) is bonded in a bent 120 degrees geometry to one Ni(4) and one P(2) atom. In the twenty-sixth O site, O(26) is bonded in an L-shaped geometry to one Ni(3) and one P(8) atom. In the twenty-seventh O site, O(27) is bonded in a distorted bent 150 degrees geometry to one Ni(1) and one P(3) atom. In the twenty-eighth O site, O(28) is bonded in a bent 120 degrees geometry to one Ni(4) and one P(8) atom.
NiP2O7 crystallizes in the triclinic P1 space group. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(12), one O(18), one O(21), one O(27), one O(5), and one O(7) atom to form NiO6 octahedra that share  a cornercorner with one Ni(3)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra,  a cornercorner with one P(5)O4 tetrahedra,  a cornercorner with one P(8)O4 tetrahedra, and corners with two equivalent P(4)O4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. The Ni(1)-O(12) bond length is 2.06 Å. The Ni(1)-O(18) bond length is 1.91 Å. The Ni(1)-O(21) bond length is 1.94 Å. The Ni(1)-O(27) bond length is 1.88 Å. The Ni(1)-O(5) bond length is 1.92 Å. The Ni(1)-O(7) bond length is 1.91 Å. In the second Ni site, Ni(2) is bonded to one O(14), one O(15), one O(16), one O(20), one O(22), and one O(8) atom to form NiO6 octahedra that share  a cornercorner with one Ni(4)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra,  a cornercorner with one P(6)O4 tetrahedra,  a cornercorner with one P(7)O4 tetrahedra, and  an edgeedge with one P(5)O4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. The Ni(2)-O(14) bond length is 1.89 Å. The Ni(2)-O(15) bond length is 1.90 Å. The Ni(2)-O(16) bond length is 1.87 Å. The Ni(2)-O(20) bond length is 2.01 Å. The Ni(2)-O(22) bond length is 1.94 Å. The Ni(2)-O(8) bond length is 1.86 Å. In the third Ni site, Ni(3) is bonded to one O(1), one O(11), one O(12), one O(17), one O(26), and one O(4) atom to form NiO6 octahedra that share  a cornercorner with one Ni(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra,  a cornercorner with one P(7)O4 tetrahedra, and  an edgeedge with one P(8)O4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. The Ni(3)-O(1) bond length is 1.86 Å. The Ni(3)-O(11) bond length is 1.89 Å. The Ni(3)-O(12) bond length is 2.01 Å. The Ni(3)-O(17) bond length is 1.87 Å. The Ni(3)-O(26) bond length is 1.94 Å. The Ni(3)-O(4) bond length is 1.90 Å. In the fourth Ni site, Ni(4) is bonded to one O(13), one O(19), one O(20), one O(25), one O(28), and one O(9) atom to form NiO6 octahedra that share  a cornercorner with one Ni(2)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra,  a cornercorner with one P(5)O4 tetrahedra,  a cornercorner with one P(7)O4 tetrahedra,  a cornercorner with one P(8)O4 tetrahedra, and corners with two equivalent P(6)O4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. The Ni(4)-O(13) bond length is 1.91 Å. The Ni(4)-O(19) bond length is 1.92 Å. The Ni(4)-O(20) bond length is 2.06 Å. The Ni(4)-O(25) bond length is 1.91 Å. The Ni(4)-O(28) bond length is 1.95 Å. The Ni(4)-O(9) bond length is 1.88 Å. There are eight inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(18), one O(23), and one O(3) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra,  a cornercorner with one Ni(3)O6 octahedra, and  a cornercorner with one P(7)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 45-53°. The P(1)-O(1) bond length is 1.56 Å. The P(1)-O(18) bond length is 1.56 Å. The P(1)-O(23) bond length is 1.48 Å. The P(1)-O(3) bond length is 1.66 Å. In the second P site, P(2) is bonded to one O(2), one O(24), one O(25), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(2)O6 octahedra,  a cornercorner with one Ni(4)O6 octahedra, and  a cornercorner with one P(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 44-54°. The P(2)-O(2) bond length is 1.48 Å. The P(2)-O(24) bond length is 1.66 Å. The P(2)-O(25) bond length is 1.56 Å. The P(2)-O(8) bond length is 1.56 Å. In the third P site, P(3) is bonded to one O(11), one O(16), one O(24), and one O(27) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra,  a cornercorner with one Ni(2)O6 octahedra,  a cornercorner with one Ni(3)O6 octahedra, and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 44-48°. The P(3)-O(11) bond length is 1.53 Å. The P(3)-O(16) bond length is 1.55 Å. The P(3)-O(24) bond length is 1.60 Å. The P(3)-O(27) bond length is 1.53 Å. In the fourth P site, P(4) is bonded to one O(10), one O(4), one O(5), and one O(7) 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(5)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 41-49°. The P(4)-O(10) bond length is 1.62 Å. The P(4)-O(4) bond length is 1.53 Å. The P(4)-O(5) bond length is 1.53 Å. The P(4)-O(7) bond length is 1.53 Å. In the fifth P site, P(5) is bonded to one O(10), one O(20), one O(21), and one O(22) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra,  a cornercorner with one Ni(4)O6 octahedra,  a cornercorner with one P(4)O4 tetrahedra, and  an edgeedge with one Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-51°. The P(5)-O(10) bond length is 1.59 Å. The P(5)-O(20) bond length is 1.60 Å. The P(5)-O(21) bond length is 1.52 Å. The P(5)-O(22) bond length is 1.54 Å. In the sixth P site, P(6) is bonded to one O(13), one O(15), one O(19), and one O(6) 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 41-49°. The P(6)-O(13) bond length is 1.53 Å. The P(6)-O(15) bond length is 1.53 Å. The P(6)-O(19) bond length is 1.53 Å. The P(6)-O(6) bond length is 1.62 Å. In the seventh P site, P(7) is bonded to one O(14), one O(17), one O(3), and one O(9) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(2)O6 octahedra,  a cornercorner with one Ni(3)O6 octahedra,  a cornercorner with one Ni(4)O6 octahedra, and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 45-48°. The P(7)-O(14) bond length is 1.53 Å. The P(7)-O(17) bond length is 1.55 Å. The P(7)-O(3) bond length is 1.60 Å. The P(7)-O(9) bond length is 1.53 Å. In the eighth P site, P(8) is bonded to one O(12), one O(26), one O(28), and one O(6) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra,  a cornercorner with one Ni(4)O6 octahedra,  a cornercorner with one P(6)O4 tetrahedra, and  an edgeedge with one Ni(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-51°. The P(8)-O(12) bond length is 1.60 Å. The P(8)-O(26) bond length is 1.54 Å. The P(8)-O(28) bond length is 1.52 Å. The P(8)-O(6) bond length is 1.59 Å. There are twenty-eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Ni(3) and one P(1) atom. In the second O site, O(2) is bonded in a single-bond geometry to one P(2) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one P(1) and one P(7) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one Ni(3) and one P(4) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Ni(1) and one P(4) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one P(6) and one P(8) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Ni(1) and one P(4) atom. In the eighth O site, O(8) is bonded in a distorted bent 150 degrees geometry to one Ni(2) and one P(2) atom. In the ninth O site, O(9) is bonded in a distorted bent 150 degrees geometry to one Ni(4) and one P(7) atom. In the tenth O site, O(10) is bonded in a bent 120 degrees geometry to one P(4) and one P(5) atom. In the eleventh O site, O(11) is bonded in a distorted bent 120 degrees geometry to one Ni(3) and one P(3) atom. In the twelfth O site, O(12) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(3), and one P(8) atom. In the thirteenth O site, O(13) is bonded in a bent 150 degrees geometry to one Ni(4) and one P(6) atom. In the fourteenth O site, O(14) is bonded in a distorted bent 120 degrees geometry to one Ni(2) and one P(7) atom. In the fifteenth O site, O(15) is bonded in a distorted bent 120 degrees geometry to one Ni(2) and one P(6) atom. In the sixteenth O site, O(16) is bonded in a bent 120 degrees geometry to one Ni(2) and one P(3) atom. In the seventeenth O site, O(17) is bonded in a bent 120 degrees geometry to one Ni(3) and one P(7) atom. In the eighteenth O site, O(18) is bonded in a bent 120 degrees geometry to one Ni(1) and one P(1) atom. In the nineteenth O site, O(19) is bonded in a bent 120 degrees geometry to one Ni(4) and one P(6) atom. In the twentieth O site, O(20) is bonded in a distorted trigonal planar geometry to one Ni(2), one Ni(4), and one P(5) atom. In the twenty-first O site, O(21) is bonded in a bent 120 degrees geometry to one Ni(1) and one P(5) atom. In the twenty-second O site, O(22) is bonded in an L-shaped geometry to one Ni(2) and one P(5) atom. In the twenty-third O site, O(23) is bonded in a single-bond geometry to one P(1) atom. In the twenty-fourth O site, O(24) is bonded in a bent 120 degrees geometry to one P(2) and one P(3) atom. In the twenty-fifth O site, O(25) is bonded in a bent 120 degrees geometry to one Ni(4) and one P(2) atom. In the twenty-sixth O site, O(26) is bonded in an L-shaped geometry to one Ni(3) and one P(8) atom. In the twenty-seventh O site, O(27) is bonded in a distorted bent 150 degrees geometry to one Ni(1) and one P(3) atom. In the twenty-eighth O site, O(28) is bonded in a bent 120 degrees geometry to one Ni(4) and one P(8) atom.