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Ultrafine aerosol particles: Long-range interactions, aggregation kinetics and structure.

机译：超细气溶胶颗粒：远程相互作用，聚集动力学和结构。

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摘要

A theoretical and computational study of ultrafine aerosol particle aggregation including the long-range van der Waals interaction force is presented. Previously, studies of aggregation have not rigorously incorporated the effects of particle interactions. The significance of this work lies in the use of physically motivated interaction potentials in calculations of aggregation. In the first part of this study, a highly accurate approximation is developed whereby, for the first time, the van der Waals energy can be calculated for any geometry. In the aggregation process considered here, the geometry of interest is an irregular aggregate of adhering, spherical primary particles and an approaching primary particle (monomer). The effect of retardation of the long-range energy is also incorporated. In the second part of this study, the effect of these retarded, long-range van der Waals interactions, particle transport and ambient pressure and temperature on aggregate-monomer collision rate constants and aggregate structure are investigated by performing molecular dynamics simulation calculations. Glassy carbon is chosen as the prototype material for the simulations.; In general, the aggregates grown with the interaction potential tend to have relatively open structures, with few branches, while the aggregates grown without the potential tend to be more compact and branched. Further, the interaction potential results in enhancements in the collision rate constants over the corresponding geometric rate constants. The effects are smaller in the transition regime than in the free molecular regime. Simulations performed with the non-retarded and the retarded interaction potential show that the percentage of relatively open aggregates, and the magnitude of the collision rate constants are greater in the latter case than in the former. An increase in temperature resulted in a collapse of aggregate structure and decrease in collision rate constants. The effects are more pronounced in the free molecular than in the transition regime. No significant difference was observed in the structure of the aggregates or in the aggregate-monomer collision rate constants as a result of changing the pressure of the simulations from 760 mm to 3040 mm.
机译：提出了包括范德华远程相互作用力在内的超细气溶胶颗粒聚集的理论和计算研究。以前，聚集研究还没有严格考虑颗粒相互作用的影响。这项工作的意义在于在聚合计算中使用物理相互作用的潜力。在本研究的第一部分中，开发了一种高度精确的近似值，从而首次可以针对任何几何形状计算范德华力。在此处考虑的聚集过程中，感兴趣的几何形状是粘附的球形初级粒子和接近的初级粒子（单体）的不规则聚集。还合并了远程能量的延迟效应。在本研究的第二部分中，通过进行分子动力学模拟计算，研究了这些延迟的，长程范德华相互作用，颗粒运输以及环境压力和温度对骨料-单体碰撞速率常数和骨料结构的影响。选择玻璃碳作为模拟的原型材料。通常，具有相互作用潜力的聚集体倾向于具有相对开放的结构，几乎没有分支，而没有潜力生长的聚集体倾向于更致密和分支。此外，相互作用势导致碰撞率常数超过相应的几何速率常数。在过渡方案中的作用比在自由分子方案中的作用小。用非延迟和滞后的相互作用势进行的模拟显示，在后一种情况下，相对开放的聚集体的百分比以及碰撞速率常数的大小要比前者大。温度升高导致骨料结构崩溃，碰撞速率常数降低。在自由分子中的效果比在过渡方案中更明显。由于模拟压力从760 mm更改为3040 mm，因此在骨料的结构或骨料-单体碰撞速率常数中均未观察到明显差异。

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