Composite Methodologies Towards Quantitative Predictions across the Periodic Table

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Angela Wilson of the University of North Texas is supported by an award from the Chemical Theory, Models and Computational Method program in the Chemistry Division to continue developing a novel ab initio composite method - the correlation consistent Composite Approach (ccCA) - that mimics the accuracy achieved by highly correlated methods such as CCSD(T), but at much reduced computational cost. The ccCA methodology is extraordinarily robust, and has been successfully applied not only to ground states, but also to excited states and transition states, to diverse chemistries, from weak interactions to highly energetic species, proving useful for both single reference and multireference wavefunction-based problems and for both metal and nonmetal compounds. The project goal is to develop and apply a family of composite approaches that can be used across the entire periodic table, thereby providing composite methodologies that are applicable to broad classes of problems and chemical systems. Energetic data is often the most critical information needed for rational analysis and design of molecular species and materials. However, one of the long-standing challenges in computational chemistry is in achieving accurate energetics, due to the limited size of molecules that can be studied routinely with high accuracy. The challenges become even more substantial for heavier main group, transition metal, and f-block metal species, where the evolution of practical, high accuracy approaches is much less developed. Ab initio composite strategies have provided a reliable means to predict accurate energetic properties for molecules through the 3d main group. This project addresses these issues by developing strategies for prediction of energetic properties of heavier elements, with application to chemical species and processes of relevance to environmental sustainability. The methods are widely disseminated to the broader scientific community through inclusion in popular computational chemistry software packages. The Wilson group provides scientific training to a broad range of students, from high school to doctoral.