On the fourth-order anharmonic equation of state of solids

The non-uniqueness of the definition of finite 'strain' is demonstrated to lead to significant ambiguities in the equation of state of elastic solids. The ambiguities are resolved by the rigorous derivation (due to Leibfried and Ludwig) of the Mie-Grüneisen equation. Closed expressions for φ0(V) and γ(V) are presented which contain no assumptions additional to those already present in the simple M-G equation. Numerical equations of state for NaCl and MgO are presented which satisfy all ultrasonic and shock-compression data. Comparison with previous tabulations for NaCI reveals small but significant discrepancies.