Na2ZnSi3O8 crystallizes in the monoclinic P2_1 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(6), and one O(7) atom. In the second Na site, Na(2) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(8) atom. Zn(1) is bonded to one O(2), one O(4), one O(5), and one O(6) atom to form ZnO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Si(3)O4 tetrahedra. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(3), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Zn(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(1), one O(6), one O(7), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Zn(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. In the third Si site, Si(3) is bonded to one O(3), one O(4), 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 Zn(1)O4 tetrahedra. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Na(1), one Na(2), one Si(1), and one Si(2) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Zn(1), and one Si(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(2), one Si(1), and one Si(3) atom. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(2), one Zn(1), and one Si(3) atom. In the fifth O site, O(5) is bonded in a distorted tetrahedral geometry to one Na(1), one Na(2), one Zn(1), and one Si(3) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Zn(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Na(1), one Si(2), and one Si(3) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Na(2), one Si(1), and one Si(2) atom.
Na2ZnSi3O8 crystallizes in the monoclinic P2_1 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(6), and one O(7) atom. The Na(1)-O(1) bond length is 2.88 Å. The Na(1)-O(2) bond length is 2.41 Å. The Na(1)-O(4) bond length is 2.63 Å. The Na(1)-O(5) bond length is 2.48 Å. The Na(1)-O(6) bond length is 2.62 Å. The Na(1)-O(7) bond length is 3.02 Å. In the second Na site, Na(2) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(8) atom. The Na(2)-O(1) bond length is 2.60 Å. The Na(2)-O(2) bond length is 2.76 Å. The Na(2)-O(3) bond length is 2.59 Å. The Na(2)-O(4) bond length is 2.37 Å. The Na(2)-O(5) bond length is 2.47 Å. The Na(2)-O(6) bond length is 2.58 Å. The Na(2)-O(8) bond length is 2.60 Å. Zn(1) is bonded to one O(2), one O(4), one O(5), and one O(6) atom to form ZnO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Si(3)O4 tetrahedra. The Zn(1)-O(2) bond length is 1.96 Å. The Zn(1)-O(4) bond length is 1.98 Å. The Zn(1)-O(5) bond length is 1.97 Å. The Zn(1)-O(6) bond length is 1.98 Å. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(3), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Zn(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. The Si(1)-O(1) bond length is 1.66 Å. The Si(1)-O(2) bond length is 1.61 Å. The Si(1)-O(3) bond length is 1.64 Å. The Si(1)-O(8) bond length is 1.65 Å. In the second Si site, Si(2) is bonded to one O(1), one O(6), one O(7), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Zn(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. The Si(2)-O(1) bond length is 1.66 Å. The Si(2)-O(6) bond length is 1.60 Å. The Si(2)-O(7) bond length is 1.65 Å. The Si(2)-O(8) bond length is 1.66 Å. In the third Si site, Si(3) is bonded to one O(3), one O(4), 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 Zn(1)O4 tetrahedra. The Si(3)-O(3) bond length is 1.67 Å. The Si(3)-O(4) bond length is 1.61 Å. The Si(3)-O(5) bond length is 1.62 Å. The Si(3)-O(7) bond length is 1.68 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Na(1), one Na(2), one Si(1), and one Si(2) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Zn(1), and one Si(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(2), one Si(1), and one Si(3) atom. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(2), one Zn(1), and one Si(3) atom. In the fifth O site, O(5) is bonded in a distorted tetrahedral geometry to one Na(1), one Na(2), one Zn(1), and one Si(3) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Zn(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Na(1), one Si(2), and one Si(3) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Na(2), one Si(1), and one Si(2) atom.