NER: Can Aluminum Nanocluster Complexes Yield Rates of Ligand Exchange at Aluminous Mineral Surfaces?

NER：铝纳米团簇复合物能否在铝矿物表面产生配体交换率？

• 批准号: 0207709
• 负责人: William Casey
• 金额: $ 9.39万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-08-01 至 2004-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0207709&HistoricalAwards=false
• 关键词: NER; Aluminum; Nanocluster; Complexes; Yield

CaseyNER-0207709This proposal was received in response to the Nanoscale Science and Engineering initiative NSF 01-157, category NER, and is co-funded by the GEO Directorate. The reactions that concern geochemists are often ligand exchange reactions, where one atom in the inner-coordination sphere of a metal is replaced with another. Even complicated processes like adsorption and mineral dissolution are really ligand-exchange reactions because the coordination number of the metal is unchanged by the process. The rates of these reactions vary enormously for different metals yet very little is known about the reaction rates at mineral surfaces, which are the key sites that affect natural water chemistry. Stated differently, the functional groups on clays and metal-hydroxide minerals are ligands too. Geochemists are coming to rely heavily on computational methods of predicting reaction properties because so many of the key reactions are difficult to probe experimentally. Unfortunately, the computational cost of predicting rates of ligand exchanges at the aqueous-mineral interface are enormous because so many atoms must be included in a realistic simulation. We pursue an alternative strategy where we attempt to establish a correlation between measured rate coefficients of water exchange ( ) in aluminum complexes and nanoparticles and structural parameters in the complexes that were calculated using ab initio methods. This correlation is novel because it is based on the easily calculated properties of the complexes instead of on the costly transition-state structures and provides a simple and computationally inexpensive way to predict rates of one of the most fundamental classes of geochemical reactions. By hypothesis, this simple approach can be extended to nanoparticles, colloids, and clays and is limited only by the feasibility of computer simulations. This research is risky because there is no guarantee that the important variables will scale with molecular size. Nevertheless, if successful, it promises an inexpensive method to predict rates of the most fundamental of reactions in aqueous media across an enormous range of molecular sizes. It is a novel and far-reaching approach because it is based on properties of ground-state structures rather than transition states.

CaseyNER-0207709该提案是响应纳米科学与工程倡议NSF 01-157，类别NER而收到的，并由GEO理事会共同资助。地球化学家关注的反应通常是配体交换反应，即金属内配位层中的一个原子被另一个原子取代。 即使是像吸附和矿物溶解这样复杂的过程也是配体交换反应，因为金属的配位数在这个过程中是不变的。 这些反应的速率对于不同的金属有很大的差异，但对矿物表面的反应速率知之甚少，而矿物表面是影响天然水化学的关键部位。 换句话说，粘土和金属氢氧化物矿物上的官能团也是配体。地球化学家们越来越依赖计算方法来预测反应性质，因为许多关键反应很难通过实验来探测。 不幸的是，在水-矿物界面处预测配体交换速率的计算成本是巨大的，因为如此多的原子必须包括在现实的模拟中。 我们追求一种替代策略，我们试图建立一个测量的水交换速率系数（）在铝配合物和纳米粒子和结构参数的配合物，使用从头计算方法计算之间的相关性。 这种相关性是新颖的，因为它是基于容易计算的性质的配合物，而不是昂贵的过渡态结构，并提供了一个简单的和计算成本低廉的方法来预测地球化学反应的最基本的类别之一的速率。 通过假设，这种简单的方法可以扩展到纳米颗粒，胶体和粘土，并且仅受计算机模拟可行性的限制。这项研究是有风险的，因为不能保证重要的变量将与分子大小成比例。 尽管如此，如果成功的话，它有望成为一种廉价的方法来预测水介质中最基本的反应速率，跨越巨大的分子尺寸范围。 这是一种新颖而深远的方法，因为它是基于基态结构而不是过渡态的性质。