Molecular dynamics simulations of liquid, interface, and ionic solvation of polarizable carbon tetrachloride

Publisher Website
Google Scholar
Abstract
In this study, we construct a nonadditive polarizable model potential to describe the intermolecular interactions between carbon tetrachloride, CCl4, based on classical molecular dynamics techniques. The potential parameters are refined to accurately describe the experimental thermodynamic and structural properties of liquid CCl4 at 298 K. We then carried out additional liquid CCl4 simulations at temperatures in the range of 250–323 K to examine the temperature dependence of the thermodynamic properties. The computed liquid densities and the enthalpies of vaporization are in excellent agreement with experimental values. The structures of liquid CCl4 can be analyzed by examining the radial distribution functions and angular distribution functions. It is found that the liquid CCl4 forms an interlocking structure and that a local orientational correlation is observed between neighboring CCl4 molecules. We also investigate the CCl4 liquid/vapor interface using this potential model. The density profile shows that the interface is not sharp at a microscopic level and has a thickness of roughly 5 Å at 273 K. The results of angular distribution function calculations suggest that CCl4 molecules do not have a preferred orientation at the interface. The calculated surface tension is 31±2 dyn/cm, in good agreement with the experimental value of 28 dyn/cm. This model potential is also used to examine the interactions between Cs+ and small (CCl4)n (n=1–6) clusters. A tetrahedral configuration is found for the minimum structure of the Cs+(CCl4)4 cluster. It is noticed that the polarization energy is the dominant component of the total interaction of these ionic clusters, indicating the importance of including explicitly the polarization in the ionic interactions. In the study of Cs+ solvation in liquid CCl4, we observe a well-defined solvation shell around the Cs+ with a coordination number of six CCl4 molecules. It is also found that Cs+ induces a strong local orientational order in liquid CCl4. Accurate ab initio electronic structure calculations were also carried out on the CCl4 dimer and the Cs+(CCl4) cluster to compare to the results from the molecular dynamics simulations.