Effectively manipulating crystal nucleation and growth is an essential issue for controlling the crystal morphology. In this work, the effect of additives on promoting crystal nucleation and growth was investigated from both thermodynamic and kinetic perspectives by using p-methylacetanilide as the model compound. Two additives with amide-terminal and halogen-terminal were selected, and it was found that they can promote the nucleation and crystal growth of p-methylacetanilide. It was found that the existence of 4-bromoacetanilide or 4-chloroacetanilide could decrease the solubility and the interfacial energy of p-methylacetanilide in ethanol, thus leading to an easier nucleation process. Furthermore, by measuring the growth rates of the (1 1 0) and (0 1̅ 1) faces of p-methylacetanilide in the absence and presence of additives, it was found that the raised supersaturation was not the only factor for crystal growth intensification. Molecular simulations revealed that the promotion effect was because the amide-terminal of additives bring the halogen-terminal to the proximity of the p-methylacetanilide surface and disrupt the absorbed ethanol layer, thus eliminating the negative influence of solvent on the surface diffusion of p-methylacetanilide.

中文翻译：

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添加剂对对甲基乙酰苯胺的成核和生长的影响及其机理

有效地控制晶体成核和生长是控制晶体形态的重要问题。在这项工作中，以对甲基乙酰胺为模型化合物，从热力学和动力学角度研究了添加剂对促进晶体成核和生长的影响。选择了具有酰胺末端和卤素末端的两种添加剂，发现它们可以促进对甲基乙酰苯胺的成核作用和晶体生长。发现4-溴对乙酰苯胺或4-氯对乙酰苯胺的存在会降低p的溶解度和界面能-甲基乙酰苯胺在乙醇中的含量，从而导致更容易的成核过程。此外，通过在不存在和存在添加剂的情况下测量对甲基乙酰苯胺的（1 1 0）和（01̅1）面的生长速率，发现提高的过饱和度不是晶体生长增强的唯一因素。分子模拟表明，促进效果是因为酰胺末端的添加剂带来的卤素末端的附近的p -methylacetanilide表面并破坏所吸收的乙醇层，从而消除了对溶剂的表面扩散的负面影响p -甲基乙酰苯胺。