Crystal structure of spinelloid II in the system Fe3O4-Fe2SiO4
Angel, Ross J.; Woodland, Alan B.
European Journal of Mineralogy Volume 10 Number 3 (1998), p. 607 - 612
published: Jun 22, 1998
manuscript accepted: Mar 3, 1998
manuscript received: Jan 14, 1998
ArtNo. ESP147051003018, Price: 29.00 €
Abstract The crystal structure of Fe2.57Si0.43O4 synthesised at 1200°C and 4.0 GPa has been determined by single-crystal X-ray diffraction at room conditions. It is isotypic with the spinelloid II structure found in the NiAhO4-Ni2SiO4 and the NiGa2O4-Ni2SiO4 systems. The space group is Imma and the cell parameters are: a = 5.85928(10) Å, b = 17.9801(3) Å, c = 8.38395(14) Å, V= 883.252(17) Å3. The structure contains two symmetrically distinct tetrahedral sites which together form T3O10 groups. Both tetrahedra are partially occupied by both Fe3+ and Si4+, with the central tetrahedral site of each group being enriched in Si4+ relative to the terminal sites. The only octahedral site bonded to the bridging oxygens of the T3O10 groups appears to be occupied by Fe2+ alone, while the remaining three distinct octahedral sites are smaller and therefore appear to contain both Fe2+ and Fe3+