Wavefunction-based quantum chemistry, particularly based on the coupled cluster (CC) or multi-reference CI/CC formalisms, is a powerful tool for predicting and explaining the structure, reactivity, and spectroscopic signatures of molecules. However, computational cost and theoretical complexity are major roadblocks in the investigation of larger, complex chemical systems. In particular, we focus our attention on the soft x-ray spectroscopy of organic molecules, complexes and liquids. A wide rand of both static and time-resolved x-ray spectroscopies covering absorption, emission, and scattering could potentially benefit from accurate quantum-chemical calculations, but large molecular size, complicated and dynamic chemical environment, and extreme energy scales present formidable problems for conventional CI/CC calculations. We discuss the latest advances in our group to address these problems, in particular the development of practical tensor factorization (tensor hypercontraction)-based methods. We also connect the theoretical design of the computational methods with the chemical reality of interacting atoms and molecules.

From tensor factorization to spectroscopic characterization

ACS Spring 2022

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