Molecular Dynamics of Heterogeneous Systems on GPUs and Their Application to Nucleation in Gas Expanding to a Vacuum

Expansion of water vapor through
a small orifice to a vacuum produces
liquid or frozen clusters which in the experiment serve as model particles
for atmospheric aerosols. Yet, there are controversies about the shape
of these clusters, suggesting that the nucleation process is not fully
understood. Such questions can be answered by molecular dynamics simulations;
however, they require microsecond-scale runs with thousands of molecules
and accurate energy conservation. The available highly parallel codes
typically utilize domain decomposition and are inefficient for heterogeneous
systems as clusters in a dilute gas. In this work, we present an implementation
of molecular dynamics on graphics processing units based on the Verlet
list and apply it to several systems for which experimental data are
available. We reproduce sufficiently sized clusters but not the experimentally
observed clusters of irregular shape.