Thermodynamics of enthalpy, volume and bulk modulus in α-Pu

The thermodynamic interrelationship between thermal and elastic properties at constant pressure has been studied from the point of view of an empirical linear relation between adiabatic bulk modulus (BS) and enthalpy increment (ΔH). A thermodynamic analysis of this linear scaling suggests several possible simple relations for expressing the isobaric temperature dependence of various thermal quantities. These approximations invoke one or more thermoelastic quantities such as Grüneisen, and Anderson–Grüneisen parameters. The proposed BS–ΔH linear relation together with the auxiliary thermoelastic relations deduced thereof constitute a self-consistent thermodynamic framework which will be useful in a critical appraisal of the internal consistency of diverse sources of thermal and elastic property data. The applicability of this framework is highlighted by modelling the available experimental data on thermal and elastic properties of α-plutonium. In particular, a successful prediction of its molar volume could be made from the recent experimental data on bulk modulus and assessed information on enthalpy increment.