Relationship between Bulk‐Modulus Temperature Dependence and Thermal Expansivity

The relationship between two anharmonic physical properties is considered: the bulk‐modulus temperature dependence (1/B) (∂B/∂T) and the thermal expansivity (1/V) (∂V/∂T). For the first, Varshni's relationship is used, which derives from an Einstein‐oscillator model of crystals. For the second, a relationship from Slater is used with a similar basis. The ratio of the two properties is found to be γ + 1, where γ denotes the usual Gröneisen parameter, Varshni's adjustable parameter s is interpreted in terms of the Gröneisen parameter, the Einstein temperature, and the atomic volume. Applied to metals, our relationship works well for those with s‐p‐electron bonding, but poorly for those where d‐electrons contribute to bonding.