Recently, we introduced a RAS-nSF-IP/EA scheme for accurately modeling strongly correlated systems with spin and spatial degeneracies. The RAS-nSF-IP/EA approach allows for unambiguous extraction of model Hamiltonian parameters and magnetic coupling information from energy gaps, providing useful physical insights at a relatively low computational cost. We now introduce an excitation-rank RAS-nSF-IP/EA code based on tensor contractions, using a diagrammatic approach to expedite sigma vector construction in the Davidson algorithm. Our code is a NumPy-based open-source package that can interface with both Psi4 and PySCF. In addition, we have implemented a Bloch effective Hamiltonian to extract coupling parameters for systems with more than two sites. We will discuss the benchmarking of our code relative to traditional string-based approaches, as well as application of our Bloch effective Hamiltonian approach to several strongly correlated systems.

Speeding up spin-flip: Tensor contractions and parameter extractions

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.