Bartolomei M, Pirani F, Marques J M C
Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas (IFFCSIC), Serrano 123, 28006 Madrid, Spain.
Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia, 06123 Perugia, Italy.
Phys Chem Chem Phys. 2019 Jul 24;21(29):16005-16016. doi: 10.1039/c9cp02658d.
Microsolvation constitutes the first step in the formation of cluster structures of molecules that surround a solute in the bulk and it allows for a deep insight into the relationship between the structure of the solvation shells and other physical properties. We propose semiempirical potential energy functions that are able to describe the interaction between K+ or Cs+ with coronene. Such functions were calibrated through the comparison with accurate estimations of the interaction between the cation and the planar hydrocarbon, obtained by means of ab initio electronic-structure calculations. By employing the potential energy functions and an evolutionary algorithm (EA), we have investigated the structure and energetics of the clusters resulting from the microsolvation of either K+ or Cs+ with coronene molecules. The reliability of the results for smaller clusters was checked by performing geometry re-optimization exploiting a suitable DFT level of theory. This has allowed for the characterization of the first solvation shells of planar molecules of coronene around an alkali-metal ion. It has also been found that the presence of metal ion impurities considerably enhances the formation of small coronene clusters leading to much stronger binding energies for heterogeneous with respect to homogeneous aggregates. These clusters could represent relevant species involved in the early stages of soot nucleation.
微溶剂化作用是形成包围本体相中溶质的分子簇结构的第一步，它有助于深入了解溶剂化壳层结构与其他物理性质之间的关系。我们提出了半经验势能函数，该函数能够描述钾离子或铯离子与并五苯之间的相互作用。通过与利用从头算电子结构计算得到的阳离子与平面烃之间相互作用的精确估计值进行比较，对这些函数进行了校准。通过使用势能函数和进化算法（EA），我们研究了钾离子或铯离子与并五苯分子微溶剂化形成的簇的结构和能量学。通过利用合适的密度泛函理论（DFT）水平进行几何结构重新优化，检验了较小簇结果的可靠性。这使得能够表征碱金属离子周围并五苯平面分子的第一溶剂化壳层。还发现金属离子杂质的存在显著增强了小并五苯簇的形成，导致异质聚集体相对于同质聚集体具有更强的结合能。这些簇可能代表了烟灰成核早期阶段涉及的相关物种。
