Bomont Jean-Marc, Costa Dino, Bretonnet Jean-Louis
Université de Lorraine, LCP-A2MC EA 3469, 1 Bd. F. Arago, Metz, France.
Dipartimento di Scienze Matematiche e Informatiche, Scienze Fisiche e Scienze della Terra, Università degli Studi di Messina, Viale F. Stagno d'Alcontres 31, 98158 Messina, Italy.
Phys Chem Chem Phys. 2020 Mar 4;22(9):5355-5365. doi: 10.1039/c9cp06710h.
In a preliminary study [Phys. Chem. Chem. Phys., 2017, 19, 15247], we have recently documented an elusive mechanism underlying the cluster formation in model fluids with microscopic competing interactions (hard-sphere two-Yukawa). This mechanism consists in a tiny rearrangement of a distant correlation peak in the local density profile. For weak attractions, this peak contributes to the shallow, long-wave oscillation typical of such fluids; as the attraction strengthens, such a portion progressively disengages from the long-range behaviour, and moving backwards takes on the character of a new shell of neighbours, falling beyond the existing ones at shorter distances. This "reversal of trend" - despite its tiny size, in comparison with the overall aspect of the density profile - is shown to precisely occur at the onset of clustering. The scope of the present study is twofold. In the first instance, we positively assess our preliminary finding. To this aim we have studied by Monte Carlo simulations different families of two-Yukawa fluids, under the same conditions investigated in the original paper, namely fixed temperature, high fluid-density and increasingly attractive strength. Apparently, the reversal of trend in spatial correlations sets as a sensitive criterion to identify the clustering threshold, complementing other common indicators, based on the modifications undergone by the low-wavevector peak in the structure factor. Secondly, we document the accuracy of the Hypernetted Chain theory in predicting the spatial rearrangement under scrutiny. This evidence paves the way to an extended investigation of the observed phenomenology by the complementary use of theoretical and simulation tools.
在一项初步研究[《物理化学化学物理》，2017年，第19卷，第15247页]中，我们最近记录了一种难以捉摸的机制，该机制是具有微观竞争相互作用（硬球双 Yukawa 势）的模型流体中团簇形成的基础。这种机制在于局部密度分布中远距离关联峰的微小重排。对于弱吸引力，该峰促成了此类流体典型的浅长波振荡；随着吸引力增强，这一部分逐渐与长程行为分离，并向后移动，呈现出一个新的相邻壳层的特征，在较短距离处落在现有壳层之外。这种“趋势反转”——尽管与密度分布的整体形态相比其规模很小——被证明恰好在团簇形成开始时发生。本研究的范围有两个方面。首先，我们肯定地评估了我们的初步发现。为此，我们通过蒙特卡罗模拟研究了不同族的双 Yukawa 流体，条件与原论文中所研究的相同，即固定温度、高流体密度和吸引力强度不断增加。显然，空间关联中的趋势反转成为识别团簇阈值的一个敏感标准，补充了基于结构因子中低波矢峰所经历的变化的其他常见指标。其次，我们记录了超网链理论在预测所研究的空间重排方面的准确性。这一证据为通过理论和模拟工具的互补使用对所观察到的现象学进行扩展研究铺平了道路。
