Quantification of surface reactivity using rate spectra

预测溶解速率的能力对于现代地球科学问题至关重要。目前的方法使用一个材料常数来计算速率。然而，实验结果表明，在相同的化学条件下，速率变异性可达三个数量级。此外，速率变异性不表现为高斯分布。从这种分布计算出的平均速率（或速率常数）几乎没有预测意义。因此，目前计算和预测利率的方法是不合适的，目前预测的应用是有风险的。目前，替代当前方法的唯一方法是速率谱的概念。速率谱是对总速率的所有贡献的频率分布。谱的积分量化了给定时间的总速率。因此，速率谱能够量化总速率及其变异性。因此，它们也为利率预测提供了适当的依据。速率谱的组成还不能从机理上理解。它们的可变性还无法解释。因此，需要进一步深入分析和了解速率谱。我们提出了一个代表性系统的速率谱随时间的分析。我们之所以选择方解石单晶，是因为这种矿物相经常在地球表面发现，而在这些环境中，涉及方解石的化学反应非常重要。提出的研究结合了实验方法和计算机模拟计算。我们还将使用表面分析和动力学蒙特卡罗（kMC）模拟的互补方法来分析大范围长度范围内的速率谱。从这些分析中，我们期望对反应速率上升的问题有更深入的了解。

The ability to predict dissolution rates is critical for modern questions in Geoscience. The current approach uses a material constant for rate calculations. However, experimental results show a rate variability of up to three orders of magnitude under identical chemical conditions. Additionally, the rate variability shows no Gaussian distribution. A mean rate (or rate constant) computed from such a distribution contains little predictive significance. As a consequence, the current approach to calculate and predict rates is not appropriate and the application of current predictions is risky. At present, the only alternative to the current approach is the concept of rate spectra. A rate spectrum is the frequency distribution of all contributions to the overall rate. The integral of the spectrum quantifies the total rate at a given time. Consequently, rate spectra are able to quantify both the total rate as well as their variability. Thus, they also provide the proper basis for rate prediction. The components of the rate spectra are not yet understand mechanistically. Their variability cannot yet be explained. Thus further research is needed to analyze and understand rate spectra in depth. We propose the analysis of rate spectra over time using a representative system. We choose calcite single crystals, because this mineral phase is often found at the Earth s surface, and chemical reactions involving calcite are very important in these environments. The proposed investigations combine experimental approaches and computer simulation calculations. We will also use complimentary methods of surface analysis and kinetic Monte Carlo (kMC) simulations to analyze rate spectra over a large range of the length scale. From these analyses we anticipate deeper insight into the problem of upscaling of reaction rates.