Mineralogy and Petrology

, Volume 36, Issue 2, pp 85–92 | Cite as

The structure of freedite, Pb8Cu(AsO3)2O3Cl5

  • F. Pertlik
Article

Summary

The structure of freedite, Pb8Cu(AsO3)2O3Cl5, [a = 13.578(2),b = 20.099(3),c = 7.465(1)Å; β = 105.73(1)°; space group C2/m; Z = 4] was determined by direct methods and Fourier summations. The refinement of the atomic coordinates and thermal parameters-the metal atoms anisotropic, the remaining atoms isotropic-yielded anR value of 0.086 (Rw = 0.061). The five crystallographically independent Pb atoms are each surrounded by three resp. four O atoms and four Cl atoms. The novel feature of this structure are formal [(AsO3)2(CuCl)2(AsO3)2] groups, in which the Cu atoms are tetrahedrally coordinated to two Cl and two As atoms [Cu-Cl = 2.43(8)Å2 × , Cu-As = 2.32(1)Å2 ×]. The mineral is considered to contain Cu(I) and As(III) atoms linked together by covalent Cu-As bonds. The formal groups mentioned are bound to the Pb atoms via Cl and O atoms.

Die Struktur des Freedits, Pb8Cu(AsO3)2O3Cl5

Zusammenfassung

Die Struktur des Freedits, Pb8Cu(AsO3)2O3Cl5, [a = 13,578(2),b = 20,099(3),c = 7,465(1)Å; β = 105,73(1); Raumgruppe C2/m;Z = 4] wurde anhand direkter Methoden und Fouriersummationen bestimmt. Die Verfeinerung der Ortskoordinaten und der Temperaturparameter - Metallatome anisotrop, übrige Atome isotrop -ergab einenR-Wert von 0,086 (Rw = 0,061). Die fünf kristallographisch verschiedenen Pb-Atome werden von drei bzw. vier O-Atomen sowie jeweils vier Cl-Atomen umgeben. Ein neues Bauprinzip dieser Struktur sind formale [(AsO3)2(CuCl)2(AsO3)2]-Gruppen, in denen die Cu-Atome durch zwei Cl- und zwei As-Atome tetraedrisch umgeben sind [Cu-Cl= 2,43(8)Å2 ×, Cu-As = 2,32(1)Å2 x]. Es wird angenommen, daß in diesem Mineral Cu(I)- und As(III)-Atome vorliegen, die über kovalente Bindungen verknüpft sind. Diese formalen Gruppen sind über die Cl- und O-Atome an die Pb Atome gebunden.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Araki T, Moore PB (1981) Dixenite, Cu1+Mn142+Fe3+(OH)6(As3+O3)5(Si4+O4)2(As5+O4): metallic [As43+Cu1+] clusters in an oxide matrix. Am Min 66: 1263–1273Google Scholar
  2. Dunn PJ, Rouse RC (1985) Freedite and thorikosite from Långban, Sweden, and Laurion, Greece: two new species related to the synthetic bismuth oxyhalides. Am Min 70: 845–848Google Scholar
  3. Gillherg M (1961) Perite, a new oxyhalide mineral from Långban, Sweden. Arkiv Mineral Geol 2: 565–570Google Scholar
  4. Giuseppetti G, Tadini C (1973) Riesame della struttura cristallina della nadorite: PbSbO2Cl. Period Mineral 42: 335–345Google Scholar
  5. ——, —— (1974): Reexamination of the crystal structure of phosgenite, Pb2Cl2(CO3). Tschermaks Min Petr Mitt 21: 101–109Google Scholar
  6. International Tables for X-ray Crystallography (1974) vol IV. The Kynoch Press, BirminghamGoogle Scholar
  7. Pannetier J, Batail P (1981) Pb4Fe3O8Cl: Synthesis, crystal structure, and thermal expansion. J Solid State Chem 39: 15–21Google Scholar
  8. Pertlik F (1986) [Cl3Cu(I)-As(III)O3]: Ein kristallchemisch neues Bauelement in der Struktur des Pb6Cu(AsO3)2Cl7. Mh Chem 117: 1257–1261Google Scholar
  9. Rouse RC, Dunn PJ (1985) The structure of thorikosite, a naturally occuring member of the bismuth oxyhalide group. J Solid State Chem 57: 389–395Google Scholar
  10. Sahl A (1970) Lead 82-A, Crystal chemistry. In:Wedepohl KH (ed) Handbook of geochemistry, vol II/5. Springer, Berlin Heidelberg New YorkGoogle Scholar
  11. Zachariasen WH (1967) A general theory of X-ray diffraction in crystals. Acta Cryst 23: 558–564Google Scholar
  12. Zemann J (1961) Die Kristallchemie des Kupfers. Fortschr Mineral 39: 59–68Google Scholar
  13. —— (1972) Copper 29-A, Crystal chemistry. In:Wedepohl KH (ed) Handbook of geochemistry, vol II/3. Springer, Berlin Heidelberg New YorkGoogle Scholar

Copyright information

© Springer-Verlag 1987

Authors and Affiliations

  • F. Pertlik
    • 1
  1. 1.Institut für Mineralogie und Kristallographie der Universität WienWienAustria

Personalised recommendations