Generalized Valence Bond Perfect-Pairing Made Versatile Through Electron-Pairs Embedding

Pastorczak, Ewa; Jensen, Hans Jørgen Aa.; Kowalski, Piotr; Pernal, Katarzyna

doi:10.1021/acs.jctc.9b00384

Cited by 15 publications

(17 citation statements)

References 64 publications

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“…The analysis performed here for model systems confirms our observations 25 , 30 that often during bond stretching the dispersion interaction in the complex can grow significantly, creating a van der Waals minimum with monomers out of their equilibrium geometries. We hope this conclusion can be used in designing experiments where the reaction is blocked or facilitated by exciting single vibration modes of substrate molecules.…”

Section: Discussionsupporting

confidence: 87%

“…The fragments can be chosen arbitrarily; for example, a single geminal can be treated as a subsystem. 30 It is worth reiterating that partitioning of GVB orbitals into unequivocal fragments of molecular systems is feasible due to the localized nature of both strongly and weakly occupied GVB orbitals. In this work, the variant of EERPA assuming a partitioning of the GVB orbitals into two fragments A and B associated with distinct monomers is used.…”

Section: The Dispersion Energy Indicatormentioning

confidence: 99%

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Dispersion Interactions between Molecules in and out of Equilibrium Geometry: Visualization and Analysis

et al. 2022

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The London dispersion interactions between systems undergoing bond breaking, twisting, or compression are not well studied due to the scarcity and the high computational cost of methods being able to describe both the dynamic correlation and the multireference character of the system. Recently developed methods based on the Generalized Valence Bond wave function, such as EERPA-GVB and SAPT(GVB) (SAPT = symmetry-adapted perturbation theory), allow one to accurately compute and analyze noncovalent interactions between multireference systems. Here, we augment this analysis by introducing a local indicator for dispersion interactions inspired by Mata and Wuttke’s Dispersion Interaction Density [ 27761924 J. Comput. Chem. 2017 38 15 23 ] applied on top of an EERPA-GVB computation. Using a few model systems, we show what insights into the nature and evolution of the dispersion interaction during bond breaking and twisting such an approach is able to offer. The new indicator can be used at a minimal cost additional to an EERPA-GVB computation and can be complemented by an energy decomposition employing the SAPT(GVB) method. We explain the physics behind the initial increase, followed by a decrease in the interaction of linear molecules upon bond stretching. Namely, the elongation of covalent bonds leads to the enhancement of attractive dispersion interactions. For even larger bond lengths, this effect is canceled by the increase of the repulsive exchange forces resulting in a suppression of the interaction and finally leading to repulsion between monomers.

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Section: Discussionsupporting

confidence: 87%

Section: The Dispersion Energy Indicatormentioning

confidence: 99%

Dispersion Interactions between Molecules in and out of Equilibrium Geometry: Visualization and Analysis

et al. 2022

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“…Intruder states also present a significant difficulty in the development of multireference coupled-cluster theories, , next to numerical instabilities and algebraic complexity. Single-reference coupled-cluster (CC) approaches introduced by Piecuch and co-workers, e.g., the CC( P ; Q ) formalism, , may be a viable alternative, as indicated by studies of interactions involving stretched intramonomer covalent bonds. , Encouraging results have recently been obtained for strongly correlated interacting systems from multiconfigurational random phase approximation theory combined with generalized valence bond method. − The multiconfiguration density functional theory (MC DFT) , methods corrected to include long-range dynamic correlation via perturbation theory, the adiabatic connection formalism, or semiempirical dispersion models are also worth mentioning, but their accuracy for noncovalent interactions remains to be rigorously assessed.…”

Section: Introductionmentioning

confidence: 99%

Symmetry-Adapted Perturbation Theory Based on Multiconfigurational Wave Function Description of Monomers

Hapka

Przybytek

Pernal

2021

J. Chem. Theory Comput.

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We present a formulation of the multiconfigurational (MC) wave function symmetry-adapted perturbation theory (SAPT). The method is applicable to noncovalent interactions between monomers which require a multiconfigurational description, in particular when the interacting system is strongly correlated or in an electronically excited state. SAPT(MC) is based on one- and two-particle reduced density matrices of the monomers and assumes the single-exchange approximation for the exchange energy contributions. Second-order terms are expressed through response properties from extended random phase approximation (ERPA). The dispersion components of SAPT(MC) have been introduced in our previous works [ Hapka M. Hapka M. 30525591 J. Chem. Theory Comput. 2019 15 1016 1027 ; Hapka M. Hapka M. 31670950 J. Chem. Theory Comput. 2019 15 6712 6723 ]. SAPT(MC) is applied either with generalized valence bond perfect pairing (GVB) or with complete active space self-consistent field (CASSCF) treatment of the monomers. We discuss two model multireference systems: the H 2 ··· H 2 dimer in out-of-equilibrium geometries and interaction between the argon atom and excited state of ethylene. Using the C 2 H 4 * ··· Ar complex as an example, we examine second-order terms arising from negative transitions in the linear response function of an excited monomer. We demonstrate that the negative-transition terms must be accounted for to ensure qualitative prediction of induction and dispersion energies and develop a procedure allowing for their computation. Factors limiting the accuracy of SAPT(MC) are discussed in comparison with other second-order SAPT schemes on a data set of small single-reference dimers.

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“…APSG has long been known to describe bond-breaking processes correctly. 40,41,[118][119][120][121][122][123][124][125][126][127][128][129] Variational APSG is equivalent to the Piris natural orbital functional PNOF5, 130,131 meaning that the APSG 2-RDM is expressible directly in terms of its 1-RDM elements. Recently, the PNOF7 functional [132][133][134][135][136][137] has shown convincing numerical results.…”

Section: Apsg: Sparsitymentioning

confidence: 99%

Density Matrices of Seniority-Zero Geminal Wavefunctions

Moisset,

Fecteau,

Johnson

2022

Preprint

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Scalar products and density matrix elements of closed-shell pair geminal wavefunctions are evaluated directly in terms of the pair amplitudes, resulting in an analogue of Wick's theorem for fermions or bosons. This expression is in general intractable, but it is shown how it becomes feasible in three distinct ways for Richardson-Gaudin (RG) states, the antisymmetrized geminal power, and the antisymmetrized product of strongly-orthogonal geminals. Dissociation curves for hydrogen chains are computed with off-shell RG states and the antisymmetrized product of interacting geminals.Both are near exact suggesting that the incorrect results observed with ground state RG states are fixable using a different RG state.

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Generalized Valence Bond Perfect-Pairing Made Versatile Through Electron-Pairs Embedding

Cited by 15 publications

References 64 publications

Dispersion Interactions between Molecules in and out of Equilibrium Geometry: Visualization and Analysis

Dispersion Interactions between Molecules in and out of Equilibrium Geometry: Visualization and Analysis

Symmetry-Adapted Perturbation Theory Based on Multiconfigurational Wave Function Description of Monomers

Density Matrices of Seniority-Zero Geminal Wavefunctions

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