Molecular structure at the surface of a polar model liquid
Johannes Dietter; Harald Morgner; Johannes Dietter; Institut für Experimentalphysik, Naturwissentschaftliche Fakultät, Universität Witten/Herdecke, Stockumer Strasse 10, D-58448 Witten, Germany; Harald Morgner; Institut für Experimentalphysik, Naturwissentschaftliche Fakultät, Universität Witten/Herdecke, Stockumer Strasse 10, D-58448 Witten, Germany
Журнал:
Journal of Physics: Condensed Matter
Дата:
1996-05-20
Аннотация:
We have simulated a liquid layer consisting of quasi-Stockmayer molecules with the molecular dynamics method. Graphical illustration of the ensemble shows that the molecules form chains. The calculation of the chain size distribution for the bulk part and for the surface of the layer shows that in the bulk part of the liquid longer chains are more likely to occur. We reason that this is due to the higher mobility of the molecules in the surface region which lowers the probability of bond formation. In addition to this we have analysed the topological correlation between chains. To do so a distance between chains has been defined to obtain a criterion for whether two chains are neighbours or not. We have examined the angles between those molecules of two neighbouring chains which are closest or between those with the lowest pair energy. It seems that there is a slight preference that the two closest molecules of the neighbouring chains align their dipoles. If the chain sizes of the two participating chains exceed three an increase in the probability that the two closest molecules antialign their dipoles can also be observed. A rise in the dipole moment intensifies this behaviour. Lowering the moment of inertia yields a decrease in the probability to antialign the neighbouring dipoles. A possible reason is the loss of stability of the antiparallel arrangement due to an increased amplitude of the rotational vibration caused by the smaller moment of inertia. However, the parallel arrangement is still a preferred orientation between the correlated dipoles.
480.4Кб