MD Simulations of Liquid Jets

DCF

In this project, we modelled the evaporation of noble gas atoms (He and Ar) from dodecane liquid jets. Using the DL_POLY software package, we 'mixed' a few noble gas atoms in an equilibrated liquid hydrocarbon containing a liquid-vacuum interace, let the system evolve, and detected any noble gas atoms leaving the bulk surface. Around 20 Angstrom above the liquid surface, we 'detected' the evapourating atoms and recored their velocities.
The group of Prof Nathanson at Madison-Wisconsin had performed related experiments and found that the noble gas atoms do not follow a Maxwell-Boltzmann distribution at the temperature of the liquid, but instead are slightly faster.

PSI

Our results:

• MD simulation confirm the sligthly non-Maxwellian behaviour in the experiments

• The effect is more pronounced for He, whereas Ar behaves very similarly to a thermal Maxwell-Boltzmann distribution

• Unlike the experimetnal data, we could also record the angular distribution, and found it to deviate from a cosine-distribution (expected for a thermal process) and skewed slightly towards evaporating atoms being ejected along the surface normal.