Sensitivity Analysis for ReaxFF Reparametrization Using the Hilbert-Schmidt Independence Criterion.

We apply a global sensitivity method, the Hilbert-Schmidt independence criterion (HSIC), to the reparametrization of a Zn/S/H ReaxFF force field to identify the most appropriate parameters for reparametrization. Parameter selection remains a challenge in this context, as high-dimensional optimizations are prone to overfitting and take a long time but selecting too few parameters leads to poor-quality force fields. We show that the HSIC correctly and quickly identifies the most sensitive parameters and that optimizations done using a small number of sensitive parameters outperform those done using a higher-dimensional reasonable-user parameter selection.

GloMPO (Globally Managed Parallel Optimization): a tool for expensive, black-box optimizations, application to ReaxFF reparameterizations.

In this work we explore the properties which make many real-life global optimization problems extremely difficult to handle, and some of the common techniques used in literature to address them. We then introduce a general optimization management tool called GloMPO (Globally Managed Parallel Optimization) to help address some of the challenges faced by practitioners. GloMPO manages and shares information between traditional optimization algorithms run in parallel.

Kinetic Modeling of a Consecutive Enzyme-Catalyzed Enantioselective Reaction in Supercritical Media.

Based on experimental data of both batch and continuous enzyme-catalyzed kinetic resolutions of (±)--1,2-cyclohexanediol in supercritical carbon dioxide, kinetic models of increasing complexity were developed to explore the strengths and drawbacks of various modeling approaches. The simplest, first-order model proved to be a good fit for the batch experimental data in regions of high reagent concentrations but failed elsewhere. A more complex system that closely follows the true mechanism was able to fit the full range of experimental data, find constant reaction rate coefficients, and was successfully used to predict the results of the same reaction run continuously in a packed bed reactor.