Deformation textures produced in diamond anvil experiments, analysed in radial diffraction geometry

Abstract

Diamond anvil cells may not only impose pressure upon a sample but also a compressive stress that produces elastic and plastic deformation of polycrystalline samples. The plastic deformation may result in texture development if the material deforms by slip or mechanical twinning, or if grains have a non-equiaxed shape. In radial diffraction geometry, texture is revealed by variation of intensity along Debye rings relative to the compression direction. Diffraction images (obtained by CCD or image plate) can be used to extract quantitative texture information. Currently the most elegant and powerful method is a modified Rietveld technique as implemented in the software package MAUD. From texture data one can evaluate the homogeneity of strain in a diamond anvil cell, the strain magnitude and deformation mechanisms, the latter by comparing observed texture patterns with results from polycrystal plasticity simulations. Some examples such as olivine, magnesiowuestite, MgSiO(3) perovskite and ε-iron are discussed.

High‐pressure, high‐temperature deformation of CaGeO3 (perovskite)±MgO aggregates: Implications for multiphase rheology of the lower mantle

“…[41] Earlier analyses on SiPv deformed in the DAC noted that texture in SiPv depends strongly on the starting materials used [e.g., Merkel et al, 2003;Wenk et al, 2006Wenk et al, , 2004. Miyagi [2009] discovered that for the SiPvþFp sample transformed from olivine, the initial sample texture is more or less random and therefore provides most robust indicators of active slip systems, which are (1 0 0)[0 1 0] orth (that is, {1 1 0}<1 1 0> pc ) and (0 0 1)<1 1 0> orth (that is, (0 0 1)<1 0 0> pc ) [Miyagi, 2009].…”

Stress Field of the Earth’s Crust

“…Merkel et al (2002) applied this method to MgO polycrystals up to 47 GPa to calculate shear strength, elastic anisotropy and texture development under stress. Currently, the most elegant and powerful method to infer quantitative texture information from radial X-ray diffraction images is the Rietveld technique (Wenk et al 2006). In this method, the wavyness of diffraction lines is used to quantify the effect of stress on lattice strains.…”

Preferred orientation in experimentally deformed stishovite: implications for deformation mechanisms

“…We laser-heated samples at pressures of 13-16 GPa in order to activate kinetics and transition quartz directly to stishovite without first transitioning to coesite or intermediate metastable SiO 2 phases that have previously been observed to nucleate at room temperature and ~21 GPa (e.g., Haines et al 2001;Kingma et al 1996;Prakapenka et al 2004). We performed experiments in radial diffraction geometry (e.g., Wenk et al 2006) rather than axial geometry in order to see variations in diffraction intensities as a function of the azimuthal angle η on Debye rings (the angle with respect to the compression direction; η = 90° is labeled in Fig. 1).…”