Accuracy in Measurements and the Temperature and Volume Dependence of Thermoelastic Parameters

To obtain the temperature T and volume V (or pressure P) dependence of the Anderson-Gruneisen parameter δ T , measurements with high sensitivity are required. We show two examples: P, V, T measurements of NaCl done with the piston cylinder and elasticity measurements of MgO using a resonance method. In both cases, the sensitivity of the measurements leads to results that provide information about δ T (η, T), where η ≡ V/V 0 and V 0 is the volume at zero pressure. We demonstrate that determination of δ T leads to understanding of the volume and temperature dependence of q = (∂ ln γ/∂ ln V) T over a broad V, T range, where γ is the Gruneisen ratio.