Molecular dynamics study of benzene-benzene and benzene-potassium ion interactions using polarizable potential models

We have constructed a polarizable potential model for benzene using molecul ar dynamics techniques. The atomic site polarizabilities for carbon and hyd rogen were taken from the recent work of Applequist [J. Phys. Chem. 97, 601 6 (1993)], which reproduced the experimental molecular polarizability of th e benzene molecule very accurately. Our model describes well the available experimental data such as the structure and thermodynamic properties of liq uid benzene and the equilibrium properties of the liquid/vapor interface of benzene. The lowest minimum-energy structure of the benzene dimer predicte d by our model has a T-shape with a potential energy of -2.5 kcal/mol. This value agrees with the experimentally obtained value (-2.4 +/- 0.4 kcal/mol ), which was determined from a high-precision ionization measurement. The c yclic minimum-energy structures are found for both the benzene trimer and t etramer clusters. The computed density profile shows that the interface is not sharp at a microscopic level and has a thickness about 5 Angstrom at 30 0 K. The calculated surface tension is 25 +/- 2 dyn/cm, which is in excelle nt agreement with the experimentally obtained value of 28 dyn/cm. The resul ts of our model also compare well with the corresponding results for benzen e obtained by Jorgensen and Severance [J. Am. Chem. Soc. 112, 4768 (1990)], who used nonpolarizable potential parameters. We also report the details o f our study of K+(C6H6)(n=1-6) clusters. We found that the polarization eff ects were quite significant in these systems. (C) 2000 American Institute o f Physics. [S0021-9606(00)50525-X].