Thermal Properties of Close-Packed Iron Determined Using Hugoniot Functions

A quadratic equation for the temperature-independent Grueneisen coefficient γ was derived by a method in which the Walsh-Christian and Mie-Grueneisen equations are combined. Some previously existing ab initio temperature Hugoniots for hexagonal close-packed solid Fe are inaccurate because the constant-volume specific heats on the Hugoniots CVH, which are related uniquely to the solutions of the quadratic equation, have values that are too small. A CVH distribution in the solid phase range was demonstrated to agree approximately with a previous ab initio distribution. In contrast, the corresponding γ distribution was significantly different from the ab initio distribution in the lower pressure region. The causes of these disagreements are clarified