Molecular Simulation of acid-induced crystal dissociation

近10年来，研究晶体成核和生长的分子模拟技术取得了重大进展，但晶体解离的反过程却很少受到关注。这尤其适用于利用酸溶解固体的研究——这一研究结合了几个挑战，迄今为止，这些挑战使得目前的建模方法无法实现这一过程。一方面，质子转移的研究需要量子计算，这限制了模拟模型的可访问时间和长度尺度。然而，统计显著性意味着扩展了大量可能的反应事件的采样和足够大的模拟模型来处理粗糙表面，包括缺口的形成和晶体解离过程中步骤的反向传播。本提案的目的是将最初为晶体成核和生长制定的Kawska-Zahn方法转移到酸诱导固体溶解的研究中。这将提供合适质子化位点的有效预测，反应事件的量子/经典建模和解离轨迹级联的有效采样-从而允许基于溶解纳米级层的深入机制研究。方法开发应伴随着对两种相当不同的系统的应用。作为示范，我们希望探索碳酸钙、磷酸盐和分子晶体在水中的解离作为pH值的功能，与卫生清洁、生物矿物塑造和肠道系统中药物化合物的吸收有关。

While molecular simulation techniques for studying crystal nucleation and growth experienced significant progress in the past 10 years, the inverse process of crystal dissociation received much less attention. This particularly holds for the investigation of dissolving solids by the help of acids – which combines several challenges that so far render such processes elusive to current modelling approaches. On the one hand, the study of proton transfers calls for quantum calculations that limit the accessible time and length scales of the simulation models. However, statistical significance implies extended sampling of large numbers of possible reaction events and sufficiently large simulation models to address rough surfaces, including the formation of notches and the back-propagation of steps during crystal dissociation. The aim of the present proposal is to transfer the Kawska-Zahn method originally formulated for crystal nucleation and growth to the study of the acid-induced dissolving of solids. This shall provide the efficient prediction of suitable protonation sites, quantum/classical modelling of reactive events and efficient sampling of cascades of dissociation trajectories – thus allowing in-depth mechanistic investigations based on dissolving nm-sized layers. Method development shall be accompanied by application to two rather different classes of systems. As demonstrators we wish to explore the dissociation of calcium carbonates, phosphates and molecular crystals in water as functions of pH, as relevant to sanitary cleaning, biomineral shaping and the uptake of pharmaceutical compounds in the intestinal system.