Oliveira Luiz Fernando L, Cuny Jérôme, Morinière Maxime, Dontot Léo, Simon Aude, Spiegelman Fernand, Rapacioli Mathias
Laboratoire de Chimie et Physique Quantiques LCPQ/IRSAMC, Université de Toulouse (UPS) and CNRS, 118 Route de Narbonne, F-31062 Toulouse, France.
Phys Chem Chem Phys. 2015 Jul 14;17(26):17079-89. doi: 10.1039/c5cp02099a.
We investigate thermodynamic properties of small water clusters adsorbed on polycyclic aromatic hydrocarbons (PAHs), which are relevant systems in the context of astrophysical and atmospheric chemistry. We present heat capacity curves computed from parallel-tempering molecular dynamics and Monte Carlo simulations that were performed using the self-consistent-charge density-functional based tight-binding method. These curves are characteristic of the phase changes occurring in the aggregates and provide useful information on the evolution of the interaction between the water molecules and the PAHs as a function of temperature. After benchmarking our approach on the water hexamer and octamer in the gas phase, we present some results for these same clusters adsorbed on coronene and circumcoronene. When compared to the curves obtained for the isolated water clusters, the phase change temperature significantly decreases for the (H2O)8-PAH clusters whereas it depends on the nature of the PAH in the case of the hexamer. We analyse these differences as connected to the relative energies of the optimized characteristic isomers and to their dynamical behavior. We also evidence the population changes of the various cluster isomers as a function of temperature.
我们研究了吸附在多环芳烃（PAHs）上的小水团簇的热力学性质，这些体系在天体物理和大气化学领域具有重要意义。我们展示了通过并行回火分子动力学和蒙特卡罗模拟计算得到的热容曲线，这些模拟是使用基于自洽电荷密度泛函紧束缚方法进行的。这些曲线是聚集体中发生的相变的特征，并且提供了关于水分子与PAHs之间相互作用随温度变化的有用信息。在对气相中的水六聚体和八聚体进行方法基准测试后，我们给出了这些相同团簇吸附在 coronene 和 circumcoronene 上的一些结果。与孤立水团簇得到的曲线相比，(H2O)8 - PAH 团簇的相变温度显著降低，而对于六聚体，相变温度则取决于 PAH 的性质。我们将这些差异分析为与优化的特征异构体的相对能量及其动力学行为有关。我们还证明了各种团簇异构体的数量随温度的变化。
