Effect of non-hydrostaticity on the α-ε transition of iron

The α-ε transition of iron was measured resistively and by X-ray in a diamond anvil cell using a variety of pressure media. The transition pressures and the hysteresis change systematically with the shear strength of the pressure medium. The width of the hysteresis varies significantly with increasing shear strength from large positive to large negative, but the hystereses in all experiments are centered around 130 k 7 kbar. The pressure interval of the forward transition increases with increasing non-hydrostaticity and provides a quantitative measure of the shear strength of a material at very high pressures.