Analysis of high pressure equations of state for hcp iron

In the present study we have used four equations of state viz. (a) the Birch-Murnaghan third order equation of state (EOS) based on the Eulerian strain, (b) the Vinet et al. EOS based on the Rydberg interatomic potential function, (c) the Shanker et al. EOS based on the Born and Huang theory of interatomic force constant and (d) the Keane's EOS based on the concept of K′∞, the value of pressure derivative of isothermal bulk modulus (K′T) in the limit of infinitely large pressure (P → ∞), to estimate the properties of hexagonal close-packed (hcp) iron at 330 GPa, the pressure at inner core boundary (ICB). The improved values of input data on volume V, isothermal bulk modulus KT and its pressure derivative K′T corresponding to room conditions (P = 0 and T = 300 K) as suggested by Stacey (2001) [Stacey, F.D., 2001. Finite strain, thermodynamics and the Earth's core. Phys. Earth Planet. Int. 128, 179-193] have been used in the present study. A comparison of the results with the seismological data at ICB pressure provides a crucial test for the equations of state used in the present study.