Thermal expansion and Grüneisen parameters for anisotropic solids

An improved definition of Gr\"uneisen parameters ^γ_μ for anisotropic solids leads to a clearer relationship with the measured thermal expansivities α_μ. The corresponding definition of mode Gr\"uneisen parameters ^γ_μⁱ expresses the contribution of mode i to α_μ, and these are related to the cubic coefficients in the potential-energy function. A phenomenological two-component model due to Gr\"uneisen is then revived in a simplified form and is shown to yield insight into the temperature dependence of α_μ. The data on tellurium are analyzed as an example.