Naphthalene crystal shape prediction from molecular dynamics simulations

We used molecular dynamics simulations to predict the steady state crystal shape of naphthalene grown from ethanol solution. The simulations were performed at constant supersaturation by utilizing a recently proposed algorithm [Perego et al., J. Chem. Phys., 2015, 142, 144113]. To bring the crystal growth within the timescale of a molecular dynamics simulation we applied well-tempered Metadynamics with a spatially constrained collective variable, which focuses the sampling on the growing layer. We estimated that the resulting steady state crystal shape corresponds to a rhombic prism, which is in line with experiments. Further, we observed that at the investigated supersaturations, the {00-1} face grows in a two step two dimensional nucleation mechanism while the considerably faster growing faces {1-10} and {20-1} grow new layers with a one step two dimensional nucleation mechanism.本研究采用分子动力学模拟（molecular dynamics simulation），预测乙醇溶液中生长的萘的稳态晶体形貌。本模拟在恒定过饱和度条件下开展，使用了近期提出的算法[Perego等人，《Journal of Chemical Physics》，2015年，第142卷，144113号文献]。为将晶体生长过程纳入分子动力学模拟的时间尺度范围，本研究应用了带有空间约束集体变量（collective variable）的回火元动力学（well-tempered Metadynamics）方法，将采样过程聚焦于生长中的晶层。经估算，所得稳态晶体形貌为菱形棱柱，与实验结果相符。此外，在本次考察的过饱和度条件下，{00-1}晶面通过两步二维成核机制完成生长，而生长速率显著更快的{1-10}与{20-1}晶面则通过一步二维成核机制生成新的晶层。