We combine density functional theory (DFT) within the local density approximation (LDA), the quasiharmonic approximation (QHA), and a model vibrational density of states (VDoS) to calculate elastic moduli and sound velocities of γ-(Fe x, Mg 1-x) 2SiO 4 (ringwoodite), the most abundant mineral of the lower Earth's transition zone (TZ). Comparison with experimental values at room-temperature and high pressure or ambient-pressure and high temperature shows good agreement with our first-principles findings. Then, we investigate the contrasts associated with the Β→γ(Fe x, Mg 1-x) 2SiO 4 transformation at pressures and temperatures relevant to the TZ. This information offers clearly defined reference values to advance the understanding of the nature of the 520km seismic discontinuity.
Bibliographical noteFunding Information:
Research supported by the NSF/EAR-1019853 and EAR-0810272 . Computations were performed using the VLab cyberinfrastructure at the Minnesota Supercomputing Institute .
- 520km discontinuity
- First principles
- Transition zone