Crystal structures of iron bearing tetrahedrite and tennantite at 25 and 250 degrees C by means of Rietveld refinement of synchrotron data
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Crystal structures of iron bearing tetrahedrite and tennantite at 25 and 250 degrees C by means of Rietveld refinement of synchrotron data. / Friese, Karen; Grzechnik, Andrzej; Makovicky, Emil; Balic Zunic, Tonci; Karup-Møller, Sven.
I: Physics and Chemistry of Minerals, Bind 35, Nr. 8, 2008, s. 455-465.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
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TY - JOUR
T1 - Crystal structures of iron bearing tetrahedrite and tennantite at 25 and 250 degrees C by means of Rietveld refinement of synchrotron data
AU - Friese, Karen
AU - Grzechnik, Andrzej
AU - Makovicky, Emil
AU - Balic Zunic, Tonci
AU - Karup-Møller, Sven
PY - 2008
Y1 - 2008
N2 - Rietveld refinement of X-ray synchrotron data was performed for two synthetic tetrahedrite samples, with 0.61 and 1.83 Fe atoms, and two synthetic tennantite samples with 0.10 and 1.23 Fe atoms p.f.u. M-12(Sb,As)(4)S-13. Measurements were performed at 25 and 250 degrees C. For both the phases, increased Fe substitution is reflected in the increased tetrahedral 'Cu1'-S distance ('Cu1' is a site of Fe substitution) and Cu2-S distances. Cu2 was refined as a split position; the Cu2-Cu2 split about the plane of the S1(2)S2 triangle is about 0.56 and 0.65 angstrom for tetrahedrite and tennantite, respectively. Cu2-Cu2 distances in the structure cavity are 2.8-2.9 angstrom. Between 25 and 250 degrees C, the lattice parameter a increased by 0.02-0.04 angstrom and the interatomic distances by 0.01 angstrom on an average. Thermal expansion coefficients of little-substituted samples are similar to those of unsubstituted samples, whereas thermal expansion appears to decrease with increasing substitution by Fe. The Cu2-Cu2 split increases at 250 degrees C by about 0.1 angstrom for tetrahedrite and by more than 0.15 angstrom for tennantite but the cage expansion is minimal so that the Cu2-Cu2 distances in the cavity decrease with temperature. Difference Fourier maps indicate that there is little residual electron density left between the two Cu2 half-sites in tetrahedrite but this inter-site density is substantially higher in tennantite. It increases with temperature, especially in the little-substituted tennantite sample.
AB - Rietveld refinement of X-ray synchrotron data was performed for two synthetic tetrahedrite samples, with 0.61 and 1.83 Fe atoms, and two synthetic tennantite samples with 0.10 and 1.23 Fe atoms p.f.u. M-12(Sb,As)(4)S-13. Measurements were performed at 25 and 250 degrees C. For both the phases, increased Fe substitution is reflected in the increased tetrahedral 'Cu1'-S distance ('Cu1' is a site of Fe substitution) and Cu2-S distances. Cu2 was refined as a split position; the Cu2-Cu2 split about the plane of the S1(2)S2 triangle is about 0.56 and 0.65 angstrom for tetrahedrite and tennantite, respectively. Cu2-Cu2 distances in the structure cavity are 2.8-2.9 angstrom. Between 25 and 250 degrees C, the lattice parameter a increased by 0.02-0.04 angstrom and the interatomic distances by 0.01 angstrom on an average. Thermal expansion coefficients of little-substituted samples are similar to those of unsubstituted samples, whereas thermal expansion appears to decrease with increasing substitution by Fe. The Cu2-Cu2 split increases at 250 degrees C by about 0.1 angstrom for tetrahedrite and by more than 0.15 angstrom for tennantite but the cage expansion is minimal so that the Cu2-Cu2 distances in the cavity decrease with temperature. Difference Fourier maps indicate that there is little residual electron density left between the two Cu2 half-sites in tetrahedrite but this inter-site density is substantially higher in tennantite. It increases with temperature, especially in the little-substituted tennantite sample.
KW - Faculty of Science
KW - tetrahedrite
KW - split trigonal planar copper positions
KW - crystal structure at 25 and 250 degrees C
KW - Rietveld refinement
KW - iron substitution
KW - tennantite
U2 - 10.1007/s00269-008-0240-8
DO - 10.1007/s00269-008-0240-8
M3 - Journal article
VL - 35
SP - 455
EP - 465
JO - Physics and Chemistry of Minerals
JF - Physics and Chemistry of Minerals
SN - 0342-1791
IS - 8
ER -
ID: 8804997