Na2Hf2Si2SO12 crystallizes in the monoclinic Cc space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 8-coordinate geometry to one O(10), one O(12), one O(4), one O(6), one O(7), one O(8), and two equivalent O(2) atoms. In the second Na site, Na(2) is bonded in a distorted hexagonal planar geometry to one O(10), one O(11), one O(12), one O(7), one O(8), and one O(9) atom. There are two inequivalent Hf sites. In the first Hf site, Hf(1) is bonded to one O(1), one O(2), one O(3), one O(7), one O(8), and one O(9) atom to form HfO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and corners with two equivalent S(1)O4 tetrahedra. In the second Hf site, Hf(2) is bonded to one O(10), one O(11), one O(12), one O(4), one O(5), and one O(6) atom to form HfO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and corners with two equivalent S(1)O4 tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(11), one O(2), one O(5), and one O(8) atom to form SiO4 tetrahedra that share corners with two equivalent Hf(1)O6 octahedra and corners with two equivalent Hf(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 21-37°. In the second Si site, Si(2) is bonded to one O(12), one O(3), one O(4), and one O(7) atom to form SiO4 tetrahedra that share corners with two equivalent Hf(1)O6 octahedra and corners with two equivalent Hf(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 19-36°. S(1) is bonded to one O(1), one O(10), one O(6), and one O(9) atom to form SO4 tetrahedra that share corners with two equivalent Hf(1)O6 octahedra and corners with two equivalent Hf(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 26-33°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Hf(1) and one S(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent Na(1), one Hf(1), and one Si(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Hf(1) and one Si(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(1), one Hf(2), and one Si(2) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Hf(2) and one Si(1) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Na(1), one Hf(2), and one S(1) atom. In the seventh O site, O(7) is bonded in a distorted trigonal pyramidal geometry to one Na(1), one Na(2), one Hf(1), and one Si(2) atom. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Hf(1), and one Si(1) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Na(2), one Hf(1), and one S(1) atom. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Hf(2), and one S(1) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Na(2), one Hf(2), and one Si(1) atom. In the twelfth O site, O(12) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(2), one Hf(2), and one Si(2) atom.
Na2Hf2Si2SO12 crystallizes in the monoclinic Cc space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 8-coordinate geometry to one O(10), one O(12), one O(4), one O(6), one O(7), one O(8), and two equivalent O(2) atoms. The Na(1)-O(10) bond length is 2.49 Å. The Na(1)-O(12) bond length is 2.40 Å. The Na(1)-O(4) bond length is 2.66 Å. The Na(1)-O(6) bond length is 3.00 Å. The Na(1)-O(7) bond length is 2.50 Å. The Na(1)-O(8) bond length is 2.40 Å. There is one shorter (2.81 Å) and one longer (2.89 Å) Na(1)-O(2) bond length. In the second Na site, Na(2) is bonded in a distorted hexagonal planar geometry to one O(10), one O(11), one O(12), one O(7), one O(8), and one O(9) atom. The Na(2)-O(10) bond length is 2.80 Å. The Na(2)-O(11) bond length is 2.51 Å. The Na(2)-O(12) bond length is 2.59 Å. The Na(2)-O(7) bond length is 2.53 Å. The Na(2)-O(8) bond length is 2.71 Å. The Na(2)-O(9) bond length is 2.76 Å. There are two inequivalent Hf sites. In the first Hf site, Hf(1) is bonded to one O(1), one O(2), one O(3), one O(7), one O(8), and one O(9) atom to form HfO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and corners with two equivalent S(1)O4 tetrahedra. The Hf(1)-O(1) bond length is 2.27 Å. The Hf(1)-O(2) bond length is 1.98 Å. The Hf(1)-O(3) bond length is 1.97 Å. The Hf(1)-O(7) bond length is 2.08 Å. The Hf(1)-O(8) bond length is 2.00 Å. The Hf(1)-O(9) bond length is 2.27 Å. In the second Hf site, Hf(2) is bonded to one O(10), one O(11), one O(12), one O(4), one O(5), and one O(6) atom to form HfO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and corners with two equivalent S(1)O4 tetrahedra. The Hf(2)-O(10) bond length is 2.21 Å. The Hf(2)-O(11) bond length is 2.05 Å. The Hf(2)-O(12) bond length is 2.09 Å. The Hf(2)-O(4) bond length is 2.02 Å. The Hf(2)-O(5) bond length is 1.99 Å. The Hf(2)-O(6) bond length is 2.14 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(11), one O(2), one O(5), and one O(8) atom to form SiO4 tetrahedra that share corners with two equivalent Hf(1)O6 octahedra and corners with two equivalent Hf(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 21-37°. The Si(1)-O(11) bond length is 1.62 Å. The Si(1)-O(2) bond length is 1.65 Å. The Si(1)-O(5) bond length is 1.63 Å. The Si(1)-O(8) bond length is 1.66 Å. In the second Si site, Si(2) is bonded to one O(12), one O(3), one O(4), and one O(7) atom to form SiO4 tetrahedra that share corners with two equivalent Hf(1)O6 octahedra and corners with two equivalent Hf(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 19-36°. The Si(2)-O(12) bond length is 1.65 Å. The Si(2)-O(3) bond length is 1.63 Å. The Si(2)-O(4) bond length is 1.64 Å. The Si(2)-O(7) bond length is 1.65 Å. S(1) is bonded to one O(1), one O(10), one O(6), and one O(9) atom to form SO4 tetrahedra that share corners with two equivalent Hf(1)O6 octahedra and corners with two equivalent Hf(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 26-33°. The S(1)-O(1) bond length is 1.46 Å. The S(1)-O(10) bond length is 1.50 Å. The S(1)-O(6) bond length is 1.49 Å. The S(1)-O(9) bond length is 1.47 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Hf(1) and one S(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent Na(1), one Hf(1), and one Si(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Hf(1) and one Si(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(1), one Hf(2), and one Si(2) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Hf(2) and one Si(1) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Na(1), one Hf(2), and one S(1) atom. In the seventh O site, O(7) is bonded in a distorted trigonal pyramidal geometry to one Na(1), one Na(2), one Hf(1), and one Si(2) atom. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Hf(1), and one Si(1) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Na(2), one Hf(1), and one S(1) atom. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Hf(2), and one S(1) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Na(2), one Hf(2), and one Si(1) atom. In the twelfth O site, O(12) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(2), one Hf(2), and one Si(2) atom.