DOE OSTI2020
NaCa2LuSi2O7F2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are four inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 5-coordinate geometry to four O2- and one F1- atom. There are a spread of Na–O bond distances ranging from 2.32–2.86 Å. The Na–F bond length is 2.45 Å. In the second Na1+ site, Na1+ is bonded to three O2- and one F1- atom to form NaO3F trigonal pyramids that share a cornercorner with one CaO6F pentagonal bipyramid, a cornercorner with one CaO4F square pyramid, a cornercorner with one SiO3F tetrahedra, and a cornercorner with one CaO4F trigonal bipyramid. There are a spread of Na–O bond distances ranging from 2.46–2.63 Å. The Na–F bond length is 2.47 Å. In the third Na1+ site, Na1+ is bonded in a 5-coordinate geometry to two O2- and three F1- atoms. There are one shorter (2.27 Å) and one longer (2.35 Å) Na–O bond lengths. There are a spread of Na–F bond distances ranging from 2.35–2.71 Å. In the fourth Na1+ site, Na1+ is bonded in a 6-coordinate geometry to three O2- and three F1- atoms. There are a spread of Na–O bond distances ranging from 2.26–2.83 Å. There are a spread of Na–F bond distances ranging from 2.44–2.67 Å. There are eight inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to six O2- and one F1- atom to form distorted CaO6F pentagonal bipyramids that share corners with three SiO4 tetrahedra, a cornercorner with one CaO4F trigonal bipyramid, a cornercorner with one NaO3F trigonal pyramid, an edgeedge with one CaO4F trigonal bipyramid, and an edgeedge with one SiO3F2 trigonal bipyramid. There are a spread of Ca–O bond distances ranging from 2.16–2.69 Å. The Ca–F bond length is 2.81 Å. In the second Ca2+ site, Ca2+ is bonded to four O2- and one F1- atom to form distorted CaO4F trigonal bipyramids that share a cornercorner with one CaO4F square pyramid, corners with two SiO4 tetrahedra, a cornercorner with one NaO3F trigonal pyramid, and an edgeedge with one CaO6F pentagonal bipyramid. There are a spread of Ca–O bond distances ranging from 2.12–2.46 Å. The Ca–F bond length is 2.29 Å. In the third Ca2+ site, Ca2+ is bonded to four O2- and one F1- atom to form distorted CaO4F trigonal bipyramids that share a cornercorner with one CaO6F pentagonal bipyramid, a cornercorner with one SiO3F2 trigonal bipyramid, and an edgeedge with one SiO4 tetrahedra. There are a spread of Ca–O bond distances ranging from 2.17–2.38 Å. The Ca–F bond length is 2.21 Å. In the fourth Ca2+ site, Ca2+ is bonded in a 2-coordinate geometry to three O2- and one F1- atom. There are a spread of Ca–O bond distances ranging from 2.16–2.79 Å. The Ca–F bond length is 2.20 Å. In the fifth Ca2+ site, Ca2+ is bonded in a 7-coordinate geometry to four O2- and two F1- atoms. There are a spread of Ca–O bond distances ranging from 2.29–2.76 Å. There are one shorter (2.25 Å) and one longer (2.35 Å) Ca–F bond lengths. In the sixth Ca2+ site, Ca2+ is bonded to four O2- and one F1- atom to form distorted CaO4F square pyramids that share a cornercorner with one SiO4 tetrahedra, a cornercorner with one CaO4F trigonal bipyramid, and a cornercorner with one NaO3F trigonal pyramid. There are a spread of Ca–O bond distances ranging from 2.21–2.53 Å. The Ca–F bond length is 2.28 Å. In the seventh Ca2+ site, Ca2+ is bonded in a 5-coordinate geometry to three O2- and two F1- atoms. There are a spread of Ca–O bond distances ranging from 2.27–2.51 Å. There are one shorter (2.27 Å) and one longer (2.34 Å) Ca–F bond lengths. In the eighth Ca2+ site, Ca2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ca–O bond distances ranging from 2.22–2.60 Å. There are four inequivalent Lu3+ sites. In the first Lu3+ site, Lu3+ is bonded in a 6-coordinate geometry to five O2- and one F1- atom. There are a spread of Lu–O bond distances ranging from 2.13–2.71 Å. The Lu–F bond length is 2.59 Å. In the second Lu3+ site, Lu3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Lu–O bond distances ranging from 2.02–2.55 Å. In the third Lu3+ site, Lu3+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Lu–O bond distances ranging from 2.05–2.51 Å. In the fourth Lu3+ site, Lu3+ is bonded in a 6-coordinate geometry to six O2- and one F1- atom. There are a spread of Lu–O bond distances ranging from 2.06–2.59 Å. The Lu–F bond length is 2.89 Å. There are eight inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded in a water-like geometry to two O2- atoms. There is one shorter (1.63 Å) and one longer (1.78 Å) Si–O bond length. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one CaO4F trigonal bipyramid. There are a spread of Si–O bond distances ranging from 1.60–1.69 Å. In the third Si4+ site, Si4+ is bonded to three O2- and two F1- atoms to form SiO3F2 trigonal bipyramids that share a cornercorner with one SiO3F tetrahedra, a cornercorner with one CaO4F trigonal bipyramid, and an edgeedge with one CaO6F pentagonal bipyramid. There are a spread of Si–O bond distances ranging from 1.60–1.87 Å. There is one shorter (1.70 Å) and one longer (1.79 Å) Si–F bond length. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one CaO6F pentagonal bipyramid, a cornercorner with one CaO4F square pyramid, a cornercorner with one SiO3F tetrahedra, and a cornercorner with one CaO4F trigonal bipyramid. There are a spread of Si–O bond distances ranging from 1.60–1.71 Å. In the fifth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share an edgeedge with one CaO4F trigonal bipyramid. There are a spread of Si–O bond distances ranging from 1.61–1.70 Å. In the sixth Si4+ site, Si4+ is bonded in a 4-coordinate geometry to two O2- and one F1- atom. There is one shorter (1.74 Å) and one longer (1.84 Å) Si–O bond length. The Si–F bond length is 1.73 Å. In the seventh Si4+ site, Si4+ is bonded to three O2- and one F1- atom to form SiO3F tetrahedra that share a cornercorner with one CaO6F pentagonal bipyramid, a cornercorner with one SiO3F2 trigonal bipyramid, and a cornercorner with one NaO3F trigonal pyramid. There is one shorter (1.60 Å) and two longer (1.64 Å) Si–O bond length. The Si–F bond length is 1.69 Å. In the eighth Si4+ site, Si4+ is bonded to three O2- and one F1- atom to form SiO3F tetrahedra that share a cornercorner with one CaO6F pentagonal bipyramid and a cornercorner with one SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.56–1.68 Å. The Si–F bond length is 1.65 Å. There are twenty-eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Ca2+ and two Si4+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+ and two Si4+ atoms. In the third O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ca2+ and two Si4+ atoms. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Lu3+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, two Ca2+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Lu3+, and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to two Ca2+, one Lu3+, and one Si4+ atom. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to two Na1+, one Ca2+, and one Lu3+ atom. In the ninth O2- site, O2- is bonded in a 1-coordinate geometry to two Ca2+ and one Si4+ atom. In the tenth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two Ca2+ and one Si4+ atom. In the eleventh O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, one Ca2+, one Lu3+, and one Si4+ atom. In the twelfth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, two Ca2+, and one Lu3+ atom. In the thirteenth O2- site, O2- is bonded to one Na1+, two Ca2+, and one Lu3+ atom to form distorted edge-sharing ONaCa2Lu tetrahedra. In the fourteenth O2- site, O2- is bonded to two Na1+, one Ca2+, and one Lu3+ atom to form distorted corner-sharing ONa2CaLu trigonal pyramids. In the fifteenth O2- site, O2- is bonded in a 3-coordinate geometry to two Ca2+ and one Lu3+ atom. In the sixteenth O2- site, O2- is bonded to one Ca2+, two Lu3+, and one Si4+ atom to form distorted OCaLu2Si trigonal pyramids that share a cornercorner with one ONa2CaLu trigonal pyramid and an edgeedge with one ONaCa2Lu tetrahedra. In the seventeenth O2- site, O2- is bonded in a 4-coordinate geometry to two Ca2+, one Lu3+, and one O2- atom. The O–O bond length is 1.50 Å. In the eighteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Ca2+, and one Si4+ atom. In the nineteenth O2- site, O2- is bonded in a 1-coordinate geometry to one Ca2+, one Si4+, and one O2- atom. In the twentieth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, two Lu3+, and one Si4+ atom. In the twenty-first O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one O2- atom. The O–O bond length is 1.51 Å. In the twenty-second O2- site, O2- is bonded in a 3-coordinate geometry to two Lu3+ and one Si4+ atom. In the twenty-third O2- site, O2- is bonded in a distorted single-bond geometry to one Ca2+, one Lu3+, one Si4+, and one O2- atom. In the twenty-fourth O2- site, O2- is bonded in a 1-coordinate geometry to one Na1+, one Ca2+, one Lu3+, and one Si4+ atom. In the twenty-fifth O2- site, O2- is bonded in a 1-coordinate geometry to one Ca2+, two Lu3+, and one Si4+ atom. In the twenty-sixth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Lu3+ and one Si4+ atom. In the twenty-seventh O2- site, O2- is bonded in a distorted single-bond geometry to one Ca2+, one Lu3+, and one Si4+ atom. In the twenty-eighth O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Ca2+, and two Si4+ atoms. There are eight inequivalent F1- sites. In the first F1- site, F1- is bonded in a 4-coordinate geometry to one Na1+, two Ca2+, and one Lu3+ atom. In the second F1- site, F1- is bonded in a 3-coordinate geometry to two Na1+ and one Si4+ atom. In the third F1- site, F1- is bonded in a bent 150 degrees geometry to one Ca2+ and one Si4+ atom. In the fourth F1- site, F1- is bonded in a 1-coordinate geometry to two Na1+, one Lu3+, and one Si4+ atom. In the fifth F1- site, F1- is bonded in a distorted trigonal planar geometry to three Ca2+ atoms. In the sixth F1- site, F1- is bonded in a 4-coordinate geometry to one Na1+ and three Ca2+ atoms. In the seventh F1- site, F1- is bonded in a distorted single-bond geometry to one Na1+ and one Si4+ atom. In the eighth F1- site, F1- is bonded in a distorted single-bond geometry to one Na1+ and one Si4+ atom.