Volume dependence of thermal expansivity for hcp iron

It is emphasized in the present study that the earlier models for the isothermal volume dependence of thermal expansivity α, developed by Tallon, Chopelas and Boehler, Anderson and Isaak, and Liu and Chen do not satisfy the thermodynamic constraint, i.e., α→0 when P→∞ or V→0. The volume dependence of isothermal Anderson–Gruneisen parameter δT has been generalized in the present study. We have formulated a relation to compute the values of volume dependence of thermal expansivity. We have calculated thermal expansivity for Thomas–Fermi model, i.e., δT∞δT∞=2/3 for K∞'=5/3 and Stacey and Davis model δT∞δT∞=2 for K∞'=3 up to a wide range of pressure 359.5 GPa for hcp iron. It is found that the present formulation satisfies the thermodynamic constraint, i.e.,α→0 when P→∞ or V→0.