Using an efficient Monte Carlo approach known as Aggregation-Volume-bias Monte Carlo with self-adaptive Umbrella Sampling and Histogram Reweighting (AVUS-HR), we obtained the nucleation free energy profile of 1-pentanol at various temperatures from 220 to 360 K. From these profiles, differences between the free energy barrier heights obtained from our simulations and those predicted by the classical nucleation theory (CNT) were calculated. Our results strongly support that the logarithm of the nucleation rate ratio between simulation (or experiment) and CNT increases almost linearly with the inverse temperature. Among the various factors that contribute to the discrepancy between simulation and CNT nucleation rates, the nonzero surface free energy of the monomer included in the CNT makes the largest contribution. On the molecular level, the simulations indicate that a gas-phase cluster of 1-pentanol molecules is relatively compact and can contain multiple hydrogen bonded aggregates of various sizes and that this aggregate size distribution depends strongly on temperature and also on the overall size of the cluster system.
Bibliographical noteFunding Information:
We thank Dr. Jan Wedekind, Dr. Marcus Ynalvez, and Dr. Philip Hopke for helpful insights. R.B.N. thanks Jerome Robles and Adam Jundt for their useful suggestions. Financial support from LSU start-up fund, the National Science Foundation (Contract Nos. CHE/MCB-0448918 and CBET-0756641), the Petroleum Research Fund, administered by the American Chemical Society (Grant No. 41933-G9), Louisiana Board of Regents Support Fund [Contract No. LEQSF(2005-08)-RD-A-02], and a Council on Research Summer Stipend Award from the LSU Office of Research and Graduate Studies are gratefully acknowledged. Part of the computer resources were provided by the Center for Computation and Technology, the Office of Computing Services at LSU, and the Louisiana Optical Network Initiative.