GronOR: Massively parallel and GPU-accelerated non-orthogonal configuration interaction for large molecular systems

Straatsma, Tjerk P.; Broer, Ria; Faraji, Shirin; Havenith, Remco W. A.; Suarez, Luis Enrique Aguilar; Kathir, R. K.; Wibowo, Meilani; Graaf, Coen de

doi:10.1063/1.5141358

Cited by 24 publications

(32 citation statements)

References 40 publications

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“…The cc‐pVDZ basis set, 41 taken from the basis set exchange library, 42–44 was used in all calculations. The calculations of the H/S matrix elements with state specific orbitals were performed with GronOR, 35–36 following the procedure outlined in Ref. 37 with both τ MO and τ det equal to 10 −5 .…”

Section: Methodsmentioning

confidence: 99%

“…In the aforementioned NOCI approach, the wavefunction for a dimer is written as a linear combination of so‐called many‐electron basis functions (MEBFs), which are spin‐adapted, antisymmetrized products of molecular wavefunctions 35–36 . Hence, in case of a dimer AB, each MEBF is a product of two molecular wavefunctions, one describing the electronic state of molecule A and one describing the electronic state of molecule B.…”

Section: Introductionmentioning

confidence: 99%

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Electronic couplings for singlet fission: Orbital choice and extrapolation to the complete basis set limit

et al. 2020

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For the search for promising singlet fission candidates, the calculation of the effective electronic coupling, which is required to estimate the singlet fission rate between the initially excited state (S0S1) and the multiexcitonic state (1TT, two triplets on neighboring molecules, coupled into a singlet), should be sufficiently reliable and fast enough to explore the configuration space. We propose here to modify the calculation of the effective electronic coupling using a nonorthogonal configuration interaction approach by: (a) using only one set of orbitals, optimized for the triplet state of the molecules, to describe all molecular electronic states, and (b) only taking the leading configurations into consideration. Furthermore, we also studied the basis set convergence of the electronic coupling, and we found, by comparison to the complete basis set limit obtained using the cc‐pVnZ series of basis sets, that both the aug‐cc‐pVDZ and 6–311++G** basis sets are a good compromise between accuracy and computational feasibility. The proposed approach enables future work on larger clusters of molecules than dimers.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electronic couplings for singlet fission: Orbital choice and extrapolation to the complete basis set limit

et al. 2020

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“…The most recent success of R. Broer and co-workers in the singlet fission world is the joint project GronOR [ 51 ], named after the working places of the project partners: University of Groningen and Oak Ridge National Laboratory. GronOR is a non-orthogonal configuration interaction (NOCI) [ 52 ] code “for describing the electronic structure of molecular assemblies in terms of individual molecular wave functions or molecular fragment wave functions” [ 53 ]. It finds its application in the process of singlet fission in terms of calculating effective electronic state couplings.…”

Section: Mechanism Rate and The Supramolecular Viewmentioning

confidence: 99%

Women in the Singlet Fission World: Pearls in a Semi-Open Shell

2021

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Singlet fission, a multiple exciton generation process, can revolutionize existing solar cell technologies. Offering the possibility to double photocurrent, the process has become a focal point for physicists, chemists, software developers, and engineers. The following review is dedicated to the female investigators, predominantly theorists, who have contributed to the field of singlet fission. We highlight their most significant advances in the subject, from deciphering the mechanism of the process to designing coveted singlet fission materials.

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“…The stack of benzene molecules represents a good ground for comparison between Stochastic GASSCF, Active Space Decomposition Density Matrix Renormalization Group (ASD-DMRG), 77,78 and Non-Orthogonal CI with a Reduced Common Molecular Orbital Basis (NOCI-RCMO), 79,80 as the latter approaches have also been tested on the same or similar model systems in earlier works. Both NOCI-RCMO and ASD-DMRG are tailored towards clusters of molecules with weak inter-space interactions, and share the assumption that the main correlation effects happen within the fragments.…”

Section: Benzene Stackmentioning

confidence: 99%

“…The NOCI-RCMO method uses orthonormal molecular orbitals for each state on each fragment but allows non-orthogonality between orbitals in different states or different fragments. 79,80 From the non-orthogonal and partly redundant orbitals, a common orbital basis is constructed on each fragment by removing linear dependencies among the orbitals in different states, depending on a cutoff value τ MO for the diagonalized overlap matrix. The common orbital bases on each fragment are then collected together to form a large non-orthogonal MO basis for the cluster.…”

Section: Benzene Stackmentioning

confidence: 99%

Stochastic Generalized Active Space Self-Consistent Field: Theory and Application

Weser

Guther

Ghanem

et al. 2021

Preprint

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An algorithm to perform stochastic generalized active space calculations, Stochastic-GAS, is presented, that uses the Slater determinant based FCIQMC algorithm as configuration interaction eigensolver. Stochastic-GAS allows the construction and stochastic optimization of preselected truncated configuration interaction wave functions, either to reduce the computational costs of large active space wave function optimizations, or to probe the role of specific electron correlation pathways. As for the conventional GAS procedure, the preselection of the truncated wave function is based on the selection of multiple active subspaces while imposing restrictions on the interspace excitations. Both local and cumulative minimum and maximum occupation number constraints are supported by Stochastic-GAS. The occupation number constraints are efficiently encoded in precomputed probability distributions, using the precomputed heat bath algorithm, which removes nearly all runtime overheads of GAS. This strategy effectively allows the FCIQMC dynamics to a priori exclude electronic configurations that are not allowed by GAS restrictions. Stochastic-GAS reduced density matrices are stochastically sampled, allowing orbital relaxations via Stochastic-GASSCF, and direct evaluation of properties that can be extracted from density matrices, such as the spin expectation value. Three test case applications have been chosen to demonstrate the flexibility of Stochastic-GAS: (a) the Stochastic-GASSCF optimization of a stack of five benzene molecules, that shows the applicability of Stochastic-GAS towards fragment-based chemical systems; (b) an uncontracted stochastic MRCISD calculation that correlates 96 electrons and 159 molecular orbitals, and uses a large (32, 34) active space reference wave function for an Fe(II)-porphyrin model system, showing how GAS can be applied to systematically recover dynamic electron correlation, and how in the specific case of the Fe(II)-porphyrin dynamic correlation further differentially stabilizes the triplet over the quintet spin state; (c) the study of an Fe4S4 cluster's spin-ladder energetics via highly truncated stochastic-GAS wave functions, where we show how GAS can be applied to understand the competing spin-exchange and charge-transfer correlating mechanisms in stabilizing different spin-states.

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GronOR: Massively parallel and GPU-accelerated non-orthogonal configuration interaction for large molecular systems

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Cited by 24 publications

References 40 publications

Electronic couplings for singlet fission: Orbital choice and extrapolation to the complete basis set limit

Electronic couplings for singlet fission: Orbital choice and extrapolation to the complete basis set limit

Women in the Singlet Fission World: Pearls in a Semi-Open Shell

Stochastic Generalized Active Space Self-Consistent Field: Theory and Application

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