(196c) Simulation of Gas-Liquid Homogeneous Nucleation: a Molecular Dynamics Study

A fundamental understanding of the nucleation process is essential to better understand and control the processes in material, atmospheric, and biological sciences associated with first order phase transitions. Since nucleation is a thermally activated process, accurate prediction of the nucleation rate is a very sensitive function of the "free energy" barrier between the two states of interest (e.g., vapor state and a liquid drop state). Although a phenomenological theory for prediction of the nucleation rate namely, the Classical Nucleation Theory (CNT) ^[1] exists, its predictions of nucleation rates are not in quantitative agreement with experimental data ^[2]. Motivated by this fact, a number of studies to date have had their focus the development of molecular theories or simulation techniques for prediction of nucleation rates ^[4-6]. In this study, a new, rigorous canonical ensemble molecular dynamics simulation approach is proposed for accurate estimation of the nucleation barrier in gas-liquid homogeneous nucleation. Simulations are performed for Lennard-Jones system due to the fact that the phase behavior of this system is well known and estimates of the classical nucleation rates have been made. Specifically, molecular dynamics simulations have been performed in periodic confined systems where Gibbs' drops have been taken as the critical nuclei. In turn, the nucleation barrier at a given supersaturation is computed using a density functional inspired thermodynamic path that connects the configurations of interest with ideal gas configurations without passing through a first order phase transition ^[3]. In this presentation, we will report our computed nucleation rates over a broad range of supersaturations. In turn, these results are compared with CNT as well as other molecular dynamics studies ^{[4, 5]}. Extension of our proposed methodology to gas-solid system will be outlined. References: 1. R. Becker and W. Doring, Ann Phys. (Leipzig) 24:, 719 (1935) 2. A. Fladerer and R. Strey, J. Chem. Phys. 124:, 164710-1 (2006) 3. S. Somasi, B. Khomami, and R. Lovett, J. Chem. Phys. 113:, 4320 (2000) 4. P. ten wolde and D. Frenkel, J. Chem. Phys. 109:, 9901 (1998) 5. A. Neimark and A. Vishnyakov, J. Phy. Chem. B 109:, 5973 (2005) 6. B. Senger, P. Schaaf, D. Corti, R. Bowles, D. Pointu, J. Voegel, and H. Reiss, J. Chem. Phys. 110:, 6438 (1999)