Molecular Dynamics Simulations of the Liquid-Vapour Interface of a Lennard-Jones Fluid (Moleculaire simulatie van het vloeistof-damp-grensvlak van een Lennard-Jones-fluïdum)

This thesis aims to complete our understanding of the interface of a liquid-vapour system. While the intermolecular arrangements of one-phase liquid and vapour systems have been previously determined by others, the detailed and complete intermolecular arrangement of the interfacial region of a liquid-vapour system has not yet been determined completely. The numerical technique used to study the intermolecular structure of the liquid-vapour interface is molecular dynamics simulation and the calculations are focussed on a Lennard-Jones fluid. For this purpose, a new type of boundary condition the shifted reflective boundary is developed. It is shown that this boundary condition creates a fixed undisturbed single planar interface allowing the detailed study of the intermolecular arrangement of the fluid particles at the interface.Next, a complete rigourous derivation of the generalised forces associated with rectangular systems in terms of boundary and virial formulations is made, whereby the boundary conditions delimiting the system are explicitly taken into account. Special emphasis is laid on the physical interpretation of the mathematical expressions resulting from the derivation.Finally, the results for the two-particle density distribution of a liquid-vapour interface are presented as a function of three variables: position, intermolecular distance and -- this in contrast to work by other authors -- the angular dependency. The numerical results are compared with existing approximative models for the two-particle density distribution and the surface tension.status: publishe