- R Roth: Max-Planck Institut für Metallforschung, Heisenbergstraße 3, D-70589 Stuttgart, Germany. Institut für Theoretische und Angewandte Physik, Universität Stuttgart, Pfaffenwaldring 57, D-70569 Stuttgart, Germany.
We combine a density functional theory (DFT) treatment of capillary evaporation in a cylindrical pore with the morphometric approach in order to study the formation and breaking of bubbles in a hydrophobically lined part of a cone. The morphometric approach, in which the grand potential of a system is described in four geometrical terms with corresponding thermodynamical coefficients, allows extrapolation or scaling from macroscopic system sizes to nanoscales. Since only a small number of fluid particles are involved in bubble formation, it is a pseudo phase transition, and the system is subjected to fluctuations between states with and without a bubble. Fluctuations are not included in a DFT treatment, which makes it possible to explore both states of the system in great detail, in contrast to computer simulations, in which averages might be obscured by fluctuations.