Local mechanical equilibrium conditions for interfaces and thin films of arbitrary shape *

A general approach to thermodynamics of arbitrarily and non-uniformly curved interfaces and films is formulated on the basis of the total non-diagonal pressure tensor including the case of external fields. The concept of a dividing surface is reformulated and generalized. The local mechanical equilibrium conditions are derived for interfaces and thin films containing not completely developed surface layers. A more general definition of the disjoining pressure is given for thin films non-uniform in thickness. The cases of flat, wedge-shaped, cylindrical and spherical films are analysed. The mechanical equilibrium condition including the disjoining and capillary pressures is derived for the surface of the transitional zone of a wetting film on a flat substrate. The results obtained are compared with the literature data.