Comparison of approximate intermolecular potentials for ab initio fragment calculations on medium sized N-heterocycles

Barcza, Bónis; Szirmai, Ádám B.; Szántó, Katalin J.; Tajti, Attila; Szalay, Péter G.

doi:10.26434/chemrxiv-2021-gv8xk

Cited by 2 publications

(17 citation statements)

References 39 publications

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“…within the Effective Fragment Potential (EFP) framework. [32][33][34] In our previous paper on the ground state of non-covalently bound complexes 16 the CHELPG (CHarges from ELectrostatic Potentials using a Grid-based) algorithm 35 was found to work well with CC methods. In the context of CHELPG the partial charges at the atomic sites are fitted to reproduce the electrostatic potential and some lower order electrostatic moments of the molecule calculated at any level of theory, hence we can apply the one used for the active fragment (e.g.…”

Section: Qm/mmmentioning

confidence: 99%

“…As in Ref. 16, in this study we test two approaches to define the effective Hamiltonian that can be used with CC methods.…”

Section: Definition Of the Effective Hamiltonianmentioning

confidence: 99%

“…From the point of view of excited states, DNA is one of such systems since the sugars and the phosphate backbone play a spectator role as the excited states of the nucleobases, which are non-covalently bound with each other, do not delocalize to these parts. 15 On the route towards developing such a fragment based method, in our previous work 16 we have investigated the possibilities of accurately obtaining the ground state potential curves of non-covalent dimers using high-level Coupled Cluster (CC) theory to describe the electronic structure of the fragments. Several schemes have been tested and we have found that both QM/MM and PbE methods, with a proper account for dispersion and Pauli repulsion ("exchange interaction") terms from the extended Effective Fragment Potential (EFP2) [17][18][19] model are capable of reproducing full dimer calculations at the same level of theory to a high accuracy.…”

Section: Introductionmentioning

confidence: 99%

“…, and ∆V 1 (r 1 , r 2 ) and several choices have been tested in our previous study. 16 This formalism can also be applied to the excited state of the complex, provided the excitation is localized on the first fragment (see e.g. Ref.…”

mentioning

confidence: 99%

“…Eventually, a corresponding ∆V i is necessary to include the missing interaction terms. Based on our experience for the ground state, 16 QM/MM and PbE approaches used with Coupled Cluster (CC) type electronic structure methods, augmented by EFP2 dispersion and Pauli repulsion [17][18][19] are able to provide proper interaction of the fragments, worth of generalizing to excited states. Second, an appropriate approximation for the excitonic or Frenkel coupling between the excited states needs also to be established.…”

mentioning

confidence: 99%

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Definition and benchmarking of ab initio fragment methods for accurate excimer potential energy surfaces

Barcza

Szirmai

Stanton

et al. 2023

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While Coupled-Cluster methods have been proven to provide an accurate description of excited electronic states, the scaling of the computational costs with the system size limits their applicability. In this study a fragment-based approach is presented which can be applied to non-covalently bound molecules with interacting chromophores localized on the fragments (so called Frankel pairs), such as $\pi$-stacked nucleobases. The interaction of the fragments is considered at two distinct points. First, the states localized on the fragments are described in the presence of the other fragment(s), for which we test two approaches. A QM/MM type method that only includes the electrostatic interaction between the fragments in the electronic structure calculations, while Pauli repulsion and dispersion effects are added separately. The other model, a Projection-based Embedding (PbE) using the Huzinaga equation includes both electrostatic and Pauli repulsion and only needs to be augmented by dispersion interactions. In both schemes the extended Effective Fragment Potential (EFP2) method of Gordon et al.~was found to provide an accurate correction for the missing terms. In the second step, the interaction of the localized chromophores is modeled for a proper description of the excitonic coupling. Here the inclusion of purely electrostatic contributions appears to be sufficient: it is found that the Coulomb part of the coupling, as evaluated using the Transition Density Cube method, provides accurate splitting of the energy of interacting chromophores above 4 \AA\ intermolecular separations.

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Section: Qm/mmmentioning

confidence: 99%

“…As in Ref. 16, in this study we test two approaches to define the effective Hamiltonian that can be used with CC methods.…”

Section: Definition Of the Effective Hamiltonianmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Definition and benchmarking of ab initio fragment methods for accurate excimer potential energy surfaces

Barcza

Szirmai

Stanton

et al. 2023

Preprint

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show abstract

Definition and benchmarking of ab initio fragment methods for accurate excimer potential energy surfaces

Barcza

Szirmai

Stanton

et al. 2023

Preprint

View full text Add to dashboard Cite

While Coupled-Cluster methods have been proven to provide an accurate description of excited electronic states, the scaling of the computational costs with the system size limits the degree for which these methods can be applied. In this study a fragment-based approach is presented for non-covalently bound molecular complexes with interacting chromophores of the fragments (so called Frenkel pairs), such as pi-stacked nucleobases. The interaction of the fragments is considered at two distinct steps. First, the states localized on the fragments are described in the presence of the other fragment(s); for this we test two approaches. One method is founded on QM/MM principles, only including the electrostatic interaction between the fragments in the electronic structure calculation with Pauli repulsion and dispersion effects added separately. The other model, a Projection-based Embedding (PbE) using the Huzinaga equation includes both electrostatic and Pauli repulsion and only needs to be augmented by dispersion interactions. In both schemes the extended Effective Fragment Potential (EFP2) method of Gordon et al. was found to provide an adequate correction for the missing terms. In the second step, the interaction of the localized chromophores is modeled for a proper description of the excitonic coupling. Here the inclusion of purely electrostatic contributions appears to be sufficient: it is found that the Coulomb part of the coupling, as evaluated by the transition density cube method, provides accurate splitting of the energies of interacting chromophores that are separated by more than 4 Angstrom.

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Comparison of approximate intermolecular potentials for ab initio fragment calculations on medium sized N-heterocycles

Cited by 2 publications

References 39 publications

Definition and benchmarking of ab initio fragment methods for accurate excimer potential energy surfaces

Definition and benchmarking of ab initio fragment methods for accurate excimer potential energy surfaces

Definition and benchmarking of ab initio fragment methods for accurate excimer potential energy surfaces

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