An anisotropic equation of state for solid solutions, with application to plagioclase

SUMMARY This paper presents a framework for building anisotropic equations of state for solid solutions. The framework satisfies the connections between elastic and thermodynamic properties required by Maxwell’s relations. It builds on a recent anisotropic equation of state for pure phases under small deviatoric stresses, adding a dependence on a vector $\boldsymbol {n}$, whose components $n_i$ contain the molar amounts of independent end-members in the solid solution. These end-members may have distinct chemical compositions, site species occupancies or electronic spin states. The high albite-anorthite (C$\bar{\text{1}}$) plagioclase solid solution is used to illustrate the formulation.