Equation of state for generalized pressure

Abstract

Chemical pressure (or ``chemical precompression'') has a similar effect on changing the properties of matter as physical pressure does. However, a suitable method to evaluate the effect of ``precompression'' on matter has not been yet proposed. Here, we propose a concept of generalized pressure $({P}_{\mathrm{G}})$ to achieve the unification of all similar pressure factors, including internal chemical pressure $({P}_{\mathrm{I}})$ and external physical pressure $({P}_{\mathrm{E}})$. The ${P}_{\mathrm{G}}$ is the ensemble of all kinds of pressure factors based on the equivalence principle in the pressure-driven volume strain of crystal lattice or any other measurable physical quantity dominated by pressure. The equation of state for generalized pressure can elucidate the equivalent relationship between the chemical and physical pressure. To verify the proposed concept, we employed a semiconductor alloy ${\mathrm{Al}}_{0.86}{\mathrm{Ga}}_{0.16}\mathrm{N}$ as the experimental model.