On the universality of phenomenological isothermal equations of state for solids

We present a test of universality for phenomenological isothermal equations of state by applying them in different types of solids. The pressure-volume relationship and the isothermal bulk modulus have been obtained using the Birch-Murnaghan third-order as well as fourth-order equation of state (EOS), the Vinet EOS and the Shanker EOS for rare gas solids (Ne, Ar), metals (Al, Cu) and diatomic solids (LiH, MgO) down to a compression of V/V-0 = 0.2. It is found that the results obtained from the Shanker EOS compare well with the corresponding values obtained from the Vinet EOS for all the solids up to very large compressions. On the other hand, the Birch-Murnaghan EOS becomes less successful at high compressions in several cases. The variation of the pressure derivative of the isothermal bulk modulus for the entire range of compression has also been studied and used to discuss the suitability of the equations of state. (C) 1999 Elsevier Science B.V. All rights reserved.