Ri Cao

Ri Cao

Postgraduate

I work with Professor Lars Hansen in rock rheology group. My DPhil topic is about looking at the viscoelasticity of upper mantle materials utilizing high-resolution techniques (SEM, HR-EBSD). Viscoelasticity is definitely significant in geodynamic scenarios such as the glacial isostatic adjustment, seismic wave propagation, and postseismic relaxation. Single crystal olivine will be chosen to do my project initially, which is the primary minerals distributed in upper mantle area. Compressional oscillation test will be utilized to squeeze the sample in order to create dislocation (screw and edge dislocation), of which the number of dislocation will be larger than that measured by torsional oscillation test. A linear relationship between applied stress and strain can be observed during the experiment.

My master project is about reproducing the structure and properties of a new mineral HAPY (hydrous aluminum bearing pyroxene) from first principal using vasp. Al/Si cation disorder has been checked (definitely exist), which would not trigger the variation of continuous calculation. X-ray powder diffraction intensity peak has been predicted(calculated) and then compared with experimental data to detect whether they are similar or not. Elastic constant has been calculated in order to get the seismic velocities (Vp, Vs and Vd), comparing with stable mantle phases at same temperature and pressure conditions and then determine whether this mineral could be seismically visible or not.