Liquid-gas interface on molecular length scales

12/06/2008, 14:15, D5-153

Patrick Levi, Institut für Theoretische Physik, Erlangen

Microfluidic devices allow for performing chemical experiments with small amounts of reactants and to observe time scales on a high resolution. But the steady miniaturisation of lab-on-a-chip technologies increases the need for an understanding of the physical properties of fluids on small length scales. To this end the liquid-gas interface of a fluid on length scales as small as the diameter of a fluid molecules demands for a proper definition. Whereas the interface is experimentally accessible through scattering experiments a theoretical understanding still lacks. We want to know where the interface between the liquid and the gas phase will be if we know the positions of the single fluid particles. Two established definitions of the interface exist but yield contradicting results. We use an alternative idea and do not search for one interface but accept all possible areas through the particle configuration space as possible interfaces and assign probabilities to each of them. We present our idea to determine these probabilities and apply it to simulation data from a Lennard-Jones liquid. We compare our results for correlation functions of the interface and the surface tension to the existing theories.