Christin Wiggers

Local order and physical properties in Olivine

The solid solution series of Olivine (Fe_xMg_1-x)₂SiO₄ (0 < x < 1) and compounds with olivine structure are considered as a source of alkalinity, a possibility for the removal of CO₂ during enhanced weathering and as a potential cathode material. Olivine with a composition of (Fe_0.1Mg_0.9)₂SiO₄ is the dominant phase of the upper mantle and one of the most abundant minerals on Earth. Members of the mineral group are commonly found in basic, ultrabasic, extrusive, and intrusive igneous rocks and in metamorphic rocks.

In the crystal structure, the divalent cations are distributed over two symmetrically independent octahedral layers. Additionally, 1/8 of the tetrahedral sites between the octahedra are occupied by Si⁴⁺. Cation partitioning has only been investigated in terms of average occupations over the two octahedral layers and is still being discussed. Possible local correlations in the metal ordering and their implications for the physical properties have been widely neglected. Therefore, in my project I am investigating the short- and long-range order in olivine, meaning possible preferences for neighbouring cations and cation distribution within the octahedral layers. I will study the effects of local interactions between the iron and magnesium layers on the physical properties, such as isotropic bulk and shear moduli as well as compressional and shear wave velocities.