General Relations between Molecular Sensitivities and Their Physical Content

Abstract The molecular Legendre transformed representations are reexamined. They correspond to alter­native sets of parameters defining the constraints imposed on the system. In the global description the molecular (equilibrium) states are defined by the global state parameter G = (N or μ) and the state function f (r) = υ(r) or n(r); N is the system number of electrons, μ its chemical potential, υ stands for the external potential due to the nuclei, and n is the electron density. In the local description, capable of defining non-equilibrium molecular density distributions, the state is defined by two state functions, g(r) = n(r) or μ (r) and f (r); here μ (r) is the local chemical potential of the electron distribution in small volume element around r. The Maxwell cross differentiation identities in both approaches, relating various molecular sensitivities, are physically interpreted. A qualitative discussion of general relations between molecular sensitivities is given and their physical content and possible applications are commented upon.