Thermomechanical equilibrium in solid-fluid systems with curved interfaces

A virtual variational approach for deducing the conditions for thermomechanical equilibrium is extended to solid-fluid systems with curved interfaces. A surface excess energy density is introduced which depends on excess entropy, number densities of the excess constituent components, the surface deformation gradient, the surface orientation and the principal curvatures. The coupling and roles of the surface stress and the Cahn–Hoffman ξ-vector in stressed solid-fluid systems is identified. Results are used to examine the case of a solid isotropic sphere immersed in a fluid.