CAVITY FORMATION FREE-ENERGIES FOR RIGID CHAINS IN HARD-SPHERE FLUIDS

Excluded-volume-anisotropy (EVA) model predictions for the cavity form ation free energies of rigid linear polyatomic chains dissolved in har d sphere fluids are tested against Monte Carlo Widom insertion simulat ion measurements performed as a function of chain length (1 less than or equal to N less than or equal to 6), the ratio of the chain bead di ameter to the solvent diameter (0 less than or equal to sigma/sigma(S) less than or equal to 3), and solvent density (0.1 less than or equal to rho sigma(S)(3) less than or equal to 0.8). The results reveal a l inear dependence of cavity formation energy on chain length for N grea ter than or equal to 2. This allows extrapolation to chain lengths lar ger than can be measured by direct insertion. EVA predictions are foun d to be in good agreement with direct simulation results as well as lo ng chain length extrapolations (up to N = 50). As an illustration of p otential practical application of these results, the EVA model is used to predict the cavity formation free energy of n-hexane dissolved in water and in the pure n-hexane liquid as a function of temperature and pressure, throughout the liquid temperature range. (C) 1998 American Institute of Physics.