Isothermal equation of state and phase stability of Fe5Si3 up to 96GPa and 3000K

摘要

The composition of Earth's core has first-order implications for understanding the thermal and chemical history of the deep Earth. The present work measures the pressure-volume equation of state of Fe5Si3 to 96GPa in a diamond anvil cell using noble gas pressure media and demonstrates that Fe5Si3 is not stable at high temperature and pressure but reappears during thermal quench. The isothermal equation of state at ambient temperature of Fe5Si3 is given by the bulk modulus K-T,K-0=167 (8) and K-T,K-0=5.1 (2), with V-0=56.29cm(3)mol(-1). At high temperatures and pressures we observed the disappearance of hexagonal Fe5Si3 diffraction peaks and the appearance of peaks corresponding to cubic FeSi and Fe3Si structures at 18GPa and at the lowest measurable temperature (similar to 1300K), indicating that Fe5Si3 is not stable at high temperature. Upon temperature quench diffraction peaks corresponding to Fe5Si3 reappear, confirming its stability at ambient temperature and high pressure.