STRESS TENSOR OF LIQUID-VAPOR STATES OF INHOMOGENEOUS FLUIDS

The theory of the stress tensor of nonuniform fluids by means of densi ty functional theory is reviewed. We present a general, symmetric, str ess tensor valid for any free energy density functional with translati onal and rotational invariance. We specialize to the nonlocal van der Waals free energy density functional. of a simple fluid and study inho mogeneous liquid-vapor coexistence states, separated by either a plana r or a spherical interface. It is shown that the stress tensor contain s all the information regarding the mechanical equilibrium of the stat e of the system. On the one hand, it leads to the expected expressions and relationships of the interfacial quantities and, on the other, it allows for a correct separation of the bulk and interfacial contribut ions to the free energy.