Downfolding from ab initio to interacting model Hamiltonians: comprehensive analysis and benchmarking of the DFT+cRPA approach

Model Hamiltonians are regularly derived from first principles to describe correlated matter. However, the standard methods for this contain a number of largely unexplored approximations. For a strongly correlated impurity model system, here we carefully compare a standard downfolding technique with...

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Veröffentlicht in:npj computational materials 2024-06, Vol.10 (1), p.129-12, Article 129
Hauptverfasser: Chang, Yueqing, van Loon, Erik G. C. P., Eskridge, Brandon, Busemeyer, Brian, Morales, Miguel A., Dreyer, Cyrus E., Millis, Andrew J., Zhang, Shiwei, Wehling, Tim O., Wagner, Lucas K., Rösner, Malte
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Sprache:eng
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Zusammenfassung:Model Hamiltonians are regularly derived from first principles to describe correlated matter. However, the standard methods for this contain a number of largely unexplored approximations. For a strongly correlated impurity model system, here we carefully compare a standard downfolding technique with the best possible ground-truth estimates for charge-neutral excited-state energies and wave functions using state-of-the-art first-principles many-body wave function approaches. To this end, we use the vanadocene molecule and analyze all downfolding aspects, including the Hamiltonian form, target basis, double-counting correction, and Coulomb interaction screening models. We find that the choice of target-space basis functions emerges as a key factor for the quality of the downfolded results, while orbital-dependent double-counting corrections diminish the quality. Background screening of the Coulomb interaction matrix elements primarily affects crystal-field excitations. Our benchmark uncovers the relative importance of each downfolding step and offers insights into the potential accuracy of minimal downfolded model Hamiltonians.
ISSN:2057-3960
2057-3960
DOI:10.1038/s41524-024-01314-6