Kinetic analysis of homogeneous droplet nucleation using large-scale molecular dynamics simulations
Kinetic analysis of homogeneous droplet nucleation using large-scale molecular dynamics simulations
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DOI：
10.1063/1.5037647
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发表时间：
2018-07-28
影响因子：
4.4
通讯作者：
Yasuoka, Kenji
中科院分区：
文献类型：
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作者：
Ayuba, Sho;Suh, Donguk;Yasuoka, Kenji
对均匀成核的研究已经进行了几十年，但在评估成核速率时，实验和理论之间存在很大的差距，因为经典成核理论（CNT）及其所有修改仍然不能完全纳入均匀成核的动力学。最近的大规模分子动力学（MD）模拟均匀成核的成核率估计在相同的数量级，在实验中获得的。这极大地改善了实验和理论之间的一致性是令人兴奋的，因为MD可以提供分子轨迹的详细信息。因此，现在可以更好地了解均匀成核的动力学。在这项研究中，大规模的MD模拟均匀成核。通过对模拟结果的动力学分析，得到了成核速率、自由能垒和临界团簇尺寸，虽然模拟直接得到的成核速率与碳纳米管计算的成核速率相差8-13个数量级，但当将分子轨道计算的参数代入经典理论时，成核速率之间的差异减小到一个数量级内。这证明了理论方程的基本公式在物理上是合理的。我们还计算了团簇形成自由能，证实了自由能垒随过饱和比的增加而减小。估计的势垒高度是由理论确定的两倍，而临界团簇尺寸显示出很好的模拟和理论之间的协议。出版社：AIP Publishing
Studies on homogeneous nucleation have been conducted for decades, but a large gap between experiment and theory persists when evaluating the nucleation rate because the classical nucleation theory (CNT) with all its modifications still cannot fully incorporate the kinetics of homogeneous nucleation. Recent large-scale molecular dynamics (MD) simulations on homogeneous nucleation estimated a nucleation rate around the same order of magnitude as that obtained in experiments. This immensely improved agreement between experiment and theory is exciting because MD can provide detailed information on molecular trajectories. Therefore, a better understanding of the kinetics of homogeneous nucleation can now be obtained. In this study, large-scale MD simulations on homogeneous nucleation were performed. Through kinetic analysis of the simulation results, the nucleation rate, free energy barrier, and critical cluster size were found. Although the nucleation rates directly obtained from the simulations differed from those calculated from the CNT by 8-13 orders of magnitude, when the parameters calculated from the molecular trajectories were substituted into the classical theory, the discrepancy between the nucleation rates decreased to within an order of magnitude. This proves that the fundamental formulation of the theoretical equation is physically sound. We also calculated the cluster formation free energy and confirmed that the free energy barrier decreases with increasing supersaturation ratio. The estimated barrier height was twice that determined by theory, whereas the critical cluster size showed very good agreement between simulation and theory. Published by AIP Publishing.