A comparison of equations of state including the generalized Rydberg EOS

In the present study we have compared the results for pressure P, isothermal bulk modulus K and its pressure derivative K′ obtained from six equations of state (EOS) using input parameters (K0 and K0′) derived from the seismic data for the core reported by Stacey and Davis. We have used three EOS based on exponential functions for potential energy due to (i) Morse, (ii) Rydberg, and (iii) Davydov, alongwith (iv) the Birch-Murnaghan third-order EOS. The results are compared with the Stacey K-primed EOS, and also with the generalized Rydberg EOS formulated recently by Stacey in order to make the original Rydberg EOS compatible with the theory of infinite pressure extrapolation. Results obtained from equations based on exponential functions are in close agreement with those from the Stacey K-primed EOS; whereas the generalized Rydberg EOS agree well with the Birch-Murnaghan EOS, an equation that some have identified as unphysical at modest compressions.