DOE OSTI2020
Tm2PbS4 crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional. there are eight inequivalent Tm3+ sites. In the first Tm3+ site, Tm3+ is bonded to six S2- atoms to form TmS6 octahedra that share a cornercorner with one TmS6 pentagonal pyramid, a cornercorner with one TmS5 square pyramid, a cornercorner with one TmS5 trigonal bipyramid, corners with two equivalent TmS4 trigonal pyramids, an edgeedge with one TmS5 square pyramid, and an edgeedge with one TmS4 trigonal pyramid. There are a spread of Tm–S bond distances ranging from 2.63–2.86 Å. In the second Tm3+ site, Tm3+ is bonded in a 5-coordinate geometry to five S2- atoms. There are a spread of Tm–S bond distances ranging from 2.58–2.89 Å. In the third Tm3+ site, Tm3+ is bonded to five S2- atoms to form TmS5 trigonal bipyramids that share a cornercorner with one TmS6 octahedra, a cornercorner with one TmS5 square pyramid, a cornercorner with one TmS4 trigonal pyramid, and an edgeedge with one TmS6 pentagonal pyramid. The corner-sharing octahedral tilt angles are 39°. There are a spread of Tm–S bond distances ranging from 2.67–2.74 Å. In the fourth Tm3+ site, Tm3+ is bonded to four S2- atoms to form distorted TmS4 trigonal pyramids that share corners with two equivalent TmS6 octahedra, a cornercorner with one TmS5 square pyramid, an edgeedge with one TmS6 pentagonal pyramid, and an edgeedge with one TmS4 trigonal pyramid. The corner-sharing octahedra tilt angles range from 38–60°. There are a spread of Tm–S bond distances ranging from 2.50–2.75 Å. In the fifth Tm3+ site, Tm3+ is bonded to five S2- atoms to form distorted TmS5 square pyramids that share a cornercorner with one TmS6 octahedra, a cornercorner with one TmS5 trigonal bipyramid, corners with three TmS4 trigonal pyramids, and an edgeedge with one TmS6 octahedra. The corner-sharing octahedral tilt angles are 51°. There are a spread of Tm–S bond distances ranging from 2.61–2.81 Å. In the sixth Tm3+ site, Tm3+ is bonded to six S2- atoms to form distorted TmS6 pentagonal pyramids that share a cornercorner with one TmS6 octahedra, an edgeedge with one TmS5 trigonal bipyramid, and edges with two TmS4 trigonal pyramids. The corner-sharing octahedral tilt angles are 54°. There are a spread of Tm–S bond distances ranging from 2.68–2.90 Å. In the seventh Tm3+ site, Tm3+ is bonded in a distorted pentagonal planar geometry to five S2- atoms. There are a spread of Tm–S bond distances ranging from 2.70–2.84 Å. In the eighth Tm3+ site, Tm3+ is bonded to four S2- atoms to form TmS4 trigonal pyramids that share corners with two equivalent TmS5 square pyramids, a cornercorner with one TmS5 trigonal bipyramid, an edgeedge with one TmS6 octahedra, an edgeedge with one TmS6 pentagonal pyramid, and an edgeedge with one TmS4 trigonal pyramid. There are a spread of Tm–S bond distances ranging from 2.57–2.75 Å. There are four inequivalent Pb2+ sites. In the first Pb2+ site, Pb2+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of Pb–S bond distances ranging from 2.71–3.59 Å. In the second Pb2+ site, Pb2+ is bonded in a 6-coordinate geometry to six S2- atoms. There are a spread of Pb–S bond distances ranging from 2.85–3.25 Å. In the third Pb2+ site, Pb2+ is bonded in a 7-coordinate geometry to seven S2- atoms. There are a spread of Pb–S bond distances ranging from 2.87–3.43 Å. In the fourth Pb2+ site, Pb2+ is bonded in a bent 150 degrees geometry to two S2- atoms. There are one shorter (2.80 Å) and one longer (3.01 Å) Pb–S bond lengths. There are sixteen inequivalent S2- sites. In the first S2- site, S2- is bonded in a distorted T-shaped geometry to three Tm3+ and one Pb2+ atom. In the second S2- site, S2- is bonded in a 1-coordinate geometry to one Tm3+, two Pb2+, and one S2- atom. The S–S bond length is 2.10 Å. In the third S2- site, S2- is bonded in a 2-coordinate geometry to two Tm3+, one Pb2+, and one S2- atom. In the fourth S2- site, S2- is bonded in a 2-coordinate geometry to two Tm3+, one Pb2+, and one S2- atom. The S–S bond length is 2.12 Å. In the fifth S2- site, S2- is bonded in a 3-coordinate geometry to three Tm3+ and one Pb2+ atom. In the sixth S2- site, S2- is bonded in a 4-coordinate geometry to one Tm3+ and three Pb2+ atoms. In the seventh S2- site, S2- is bonded in a 5-coordinate geometry to three Tm3+ and two Pb2+ atoms. In the eighth S2- site, S2- is bonded to three Tm3+ and one Pb2+ atom to form distorted corner-sharing STm3Pb trigonal pyramids. In the ninth S2- site, S2- is bonded in a 4-coordinate geometry to four Tm3+ and one Pb2+ atom. In the tenth S2- site, S2- is bonded in a distorted bent 120 degrees geometry to two Tm3+ and two Pb2+ atoms. In the eleventh S2- site, S2- is bonded in a 4-coordinate geometry to two Tm3+ and two Pb2+ atoms. In the twelfth S2- site, S2- is bonded in a 3-coordinate geometry to three Tm3+ and one Pb2+ atom. In the thirteenth S2- site, S2- is bonded in a 3-coordinate geometry to three Tm3+ and two Pb2+ atoms. In the fourteenth S2- site, S2- is bonded in a 1-coordinate geometry to one Tm3+, two Pb2+, and one S2- atom. In the fifteenth S2- site, S2- is bonded in a 3-coordinate geometry to three Tm3+ and one Pb2+ atom. In the sixteenth S2- site, S2- is bonded to four Tm3+ atoms to form distorted corner-sharing STm4 trigonal pyramids.