Accurate Many-Body Electronic-Structure Methods for Extended Molecular Assemblies

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Edward Valeev of Virginia Tech is supported by an award from the Chemical Theory, Models and Computational Methods program in the Chemistry Division, the Condensed Matter and Materials Theory program in the Division of Materials Research and the Computational and Data-Enabled Science and Engineering Program (CDS&E) to develop radically improved understanding of electrons in molecules and materials. Electrons are the universal "glue" that holds together molecules and materials and thus determine their most relevant properties. Predicting the behavior of electrons is of fundamental importance to chemistry and materials science. The new computational approaches being developed in this project will allow scientists to see with an unprecedented degree of precision the delicate details of the dance of electrons in molecules. The new models will then help to explain how some new fascinating materials are able to chemically transform carbon dioxide, a major greenhouse gas, into valuable products. The long-term objective of this project is to design on the computer -- rather than discover by trial-and-error -- new chemical processes and new materials that help improve our everyday lives. Valeev and his research group develop software that is freely available to the research community.The technical focus of this project is on new, efficient computational methods for describing the electrons in their ground and excited states in large molecular assemblies (100-500 atoms) with the level of confidence only accessible for small molecules (5-10 atoms). These objectives are achieved by using more efficient numerical representations for electronic states, such as explicitly correlated numerical representations that model short-range correlations of pairs of electrons much more efficiently than standard approaches, and reduced-scaling representations that take advantage of the short-sightedness of the electron correlations. These ideas will be also leveraged to couple "weak" (short-range) electron correlations into models describing "strong" (long-range) correlations, such as configuration expansion or renormalization group approaches. This work has a chance to substantially change the state of the art of accurate electronic structure methods by making them a practical alternative to the currently dominant density functional methods. The algorithms and methods developed in this research will result in open-source publicly-available computer software for doing quantum mechanical modeling of large molecular systems.