Li2NiSi2O6 crystallizes in the triclinic P-1 space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded in a 5-coordinate geometry to one O(1), one O(4), one O(5), and two equivalent O(7) atoms. In the second Li site, Li(2) is bonded in a 5-coordinate geometry to one O(1), one O(4), one O(5), and two equivalent O(6) atoms. Ni(1) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form NiO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(4), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Ni(1)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Ni(1)O4 tetrahedra. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Li(1), one Li(2), one Si(1), and one Si(2) atom. In the second O site, O(2) is bonded in a linear geometry to two equivalent Si(1) atoms. In the third O site, O(3) is bonded in a linear geometry to two equivalent Si(2) atoms. In the fourth O site, O(4) is bonded to one Li(1), one Li(2), one Ni(1), and one Si(1) atom to form a mixture of distorted edge and corner-sharing OLi2SiNi trigonal pyramids. In the fifth O site, O(5) is bonded to one Li(1), one Li(2), one Ni(1), and one Si(2) atom to form a mixture of distorted edge and corner-sharing OLi2SiNi trigonal pyramids. In the sixth O site, O(6) is bonded to two equivalent Li(2), one Ni(1), and one Si(1) atom to form a mixture of distorted edge and corner-sharing OLi2SiNi trigonal pyramids. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to two equivalent Li(1), one Ni(1), and one Si(2) atom.
Li2NiSi2O6 crystallizes in the triclinic P-1 space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded in a 5-coordinate geometry to one O(1), one O(4), one O(5), and two equivalent O(7) atoms. The Li(1)-O(1) bond length is 2.41 Å. The Li(1)-O(4) bond length is 2.08 Å. The Li(1)-O(5) bond length is 2.01 Å. There is one shorter (1.98 Å) and one longer (2.52 Å) Li(1)-O(7) bond length. In the second Li site, Li(2) is bonded in a 5-coordinate geometry to one O(1), one O(4), one O(5), and two equivalent O(6) atoms. The Li(2)-O(1) bond length is 2.40 Å. The Li(2)-O(4) bond length is 2.02 Å. The Li(2)-O(5) bond length is 2.09 Å. There is one shorter (1.98 Å) and one longer (2.51 Å) Li(2)-O(6) bond length. Ni(1) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form NiO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. The Ni(1)-O(4) bond length is 2.01 Å. The Ni(1)-O(5) bond length is 2.01 Å. The Ni(1)-O(6) bond length is 2.00 Å. The Ni(1)-O(7) bond length is 2.00 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(4), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Ni(1)O4 tetrahedra. The Si(1)-O(1) bond length is 1.67 Å. The Si(1)-O(2) bond length is 1.63 Å. The Si(1)-O(4) bond length is 1.63 Å. The Si(1)-O(6) bond length is 1.63 Å. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Ni(1)O4 tetrahedra. The Si(2)-O(1) bond length is 1.67 Å. The Si(2)-O(3) bond length is 1.63 Å. The Si(2)-O(5) bond length is 1.63 Å. The Si(2)-O(7) bond length is 1.63 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Li(1), one Li(2), one Si(1), and one Si(2) atom. In the second O site, O(2) is bonded in a linear geometry to two equivalent Si(1) atoms. In the third O site, O(3) is bonded in a linear geometry to two equivalent Si(2) atoms. In the fourth O site, O(4) is bonded to one Li(1), one Li(2), one Ni(1), and one Si(1) atom to form a mixture of distorted edge and corner-sharing OLi2SiNi trigonal pyramids. In the fifth O site, O(5) is bonded to one Li(1), one Li(2), one Ni(1), and one Si(2) atom to form a mixture of distorted edge and corner-sharing OLi2SiNi trigonal pyramids. In the sixth O site, O(6) is bonded to two equivalent Li(2), one Ni(1), and one Si(1) atom to form a mixture of distorted edge and corner-sharing OLi2SiNi trigonal pyramids. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to two equivalent Li(1), one Ni(1), and one Si(2) atom.