Isothermal compression of magnetite to 320 KB

The effect of pressure on the lattice parameter of magnetite has been determined at room temperature up to 320 kbar by means of X ray diffraction employing a diamond anvil high-pressure cell. By using the Birch-Murnaghan equation with a (∂KT/∂P)T∣P=0 value of 4 ± 0.4 the isothermal bulk modulus at zero pressure was calculated to be 1.83 ± 0.10 Mbar. The X ray diffraction study also revealed that at pressures greater than 250 kbar, magnetite transforms to a high-pressure phase, which reverts to magnetite at pressures below 50 kbar. It is possible to index this high-pressure phase as being monoclinic. If it is assumed that the unit cell contains two molecules, the density is in agreement with the density predicted for a phase of Fe3O4 having all of the iron atoms in sixfold coordination.