MOLECULAR-DYNAMICS SIMULATIONS OF LIQUID, INTERFACE, AND IONIC SOLVATION OF POLARIZABLE CARBON-TETRACHLORIDE

In this study, we construct st nonadditive polarizable model potential to describe the intermolecular interactions between carbon tetrachlor ide, CCl4, based on classical molecular dynamics techniques. The poten tial parameters are refined to accurately describe the experimental th ermodynamic 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 therm odynamic properties. The computed liquid densities and the enthalpies of vaporization are in excellent agreement with experimental values. T he structures of liquid CCl4 can be analyzed by examining the radial d istribution 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 molecul es. We also investigate the CCl4 liquid/vapor interface using this pot ential model. The density profile shows that the interface is not shar p at a microscopic level and has a thickness of roughly 5 Angstrom at 273 K. The results of angular distribution function calculations sugge st that CCl4 molecules do not have a preferred orientation at the inte rface. The calculated surface tension is 31 +/- 2 dyn/cm, in good agre ement with the experimental value of 28 dyn/cm. This model potential i s also used to examine the interactions between Cs+ and small (CC1(4)) (n) (n = 1-6) clusters. A tetrahedral configuration is found for the m inimum structure of the Cs+(CCl4)(4) cluster. It is noticed that the p olarization energy is the dominant component of the total interaction of these ionic clusters, indicating the importance of including explic itly the polarization in the ionic interactions. In the study of Cs+ s olvation in liquid CCl4, we observe a well-defined solvation shell aro und the Cs+ with a coordination number of six CCl4 molecules. It is al so found that Cs+ induces a strong, local orientational order in Liqui d 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. (C) 1995 America n Institute of Physics.