Hg2Te2O7 crystallizes in the monoclinic C2/c space group. There are four inequivalent Hg sites. In the first Hg site, Hg(1) is bonded in a square co-planar geometry to two equivalent O(4) and two equivalent O(6) atoms. In the second Hg site, Hg(2) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. In the third Hg site, Hg(3) is bonded in a linear geometry to two equivalent O(2) atoms. In the fourth Hg site, Hg(4) is bonded to two equivalent O(5), two equivalent O(6), and two equivalent O(7) atoms to form distorted HgO6 pentagonal pyramids that share corners with two equivalent Te(1)O6 octahedra and corners with two equivalent Te(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-56°. There are three inequivalent Te sites. In the first Te site, Te(1) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms to form TeO6 octahedra that share corners with two equivalent Te(2)O6 octahedra and corners with two equivalent Hg(4)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 37°. In the second Te site, Te(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(7) atoms to form TeO6 octahedra that share corners with two equivalent Te(1)O6 octahedra and corners with two equivalent Hg(4)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 37°. In the third Te site, Te(3) is bonded in a distorted see-saw-like geometry to one O(2), one O(3), one O(5), and one O(6) atom. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Te(1) and one Te(2) atom. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Hg(2), one Hg(3), and one Te(3) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Hg(2), one Te(2), and one Te(3) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Hg(1), one Hg(2), and one Te(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Hg(4), one Te(1), and one Te(3) atom. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Hg(1), one Hg(4), and one Te(3) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one Hg(4) and one Te(2) atom.
Hg2Te2O7 crystallizes in the monoclinic C2/c space group. There are four inequivalent Hg sites. In the first Hg site, Hg(1) is bonded in a square co-planar geometry to two equivalent O(4) and two equivalent O(6) atoms. Both Hg(1)-O(4) bond lengths are 2.47 Å. Both Hg(1)-O(6) bond lengths are 2.19 Å. In the second Hg site, Hg(2) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. Both Hg(2)-O(2) bond lengths are 2.53 Å. Both Hg(2)-O(3) bond lengths are 2.69 Å. Both Hg(2)-O(4) bond lengths are 2.22 Å. In the third Hg site, Hg(3) is bonded in a linear geometry to two equivalent O(2) atoms. Both Hg(3)-O(2) bond lengths are 2.09 Å. In the fourth Hg site, Hg(4) is bonded to two equivalent O(5), two equivalent O(6), and two equivalent O(7) atoms to form distorted HgO6 pentagonal pyramids that share corners with two equivalent Te(1)O6 octahedra and corners with two equivalent Te(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-56°. Both Hg(4)-O(5) bond lengths are 2.51 Å. Both Hg(4)-O(6) bond lengths are 2.43 Å. Both Hg(4)-O(7) bond lengths are 2.32 Å. There are three inequivalent Te sites. In the first Te site, Te(1) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms to form TeO6 octahedra that share corners with two equivalent Te(2)O6 octahedra and corners with two equivalent Hg(4)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 37°. Both Te(1)-O(1) bond lengths are 1.98 Å. Both Te(1)-O(4) bond lengths are 1.95 Å. Both Te(1)-O(5) bond lengths are 1.98 Å. In the second Te site, Te(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(7) atoms to form TeO6 octahedra that share corners with two equivalent Te(1)O6 octahedra and corners with two equivalent Hg(4)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 37°. Both Te(2)-O(1) bond lengths are 2.00 Å. Both Te(2)-O(3) bond lengths are 1.96 Å. Both Te(2)-O(7) bond lengths are 1.94 Å. In the third Te site, Te(3) is bonded in a distorted see-saw-like geometry to one O(2), one O(3), one O(5), and one O(6) atom. The Te(3)-O(2) bond length is 1.96 Å. The Te(3)-O(3) bond length is 2.09 Å. The Te(3)-O(5) bond length is 2.17 Å. The Te(3)-O(6) bond length is 1.93 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Te(1) and one Te(2) atom. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Hg(2), one Hg(3), and one Te(3) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Hg(2), one Te(2), and one Te(3) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Hg(1), one Hg(2), and one Te(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Hg(4), one Te(1), and one Te(3) atom. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Hg(1), one Hg(4), and one Te(3) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one Hg(4) and one Te(2) atom.