A Lagrange multiplier approach for excited state properties through intermediate Hamiltonian formulation of Fock space multireference coupled-cluster theory

Gupta, Jitendra; Vaval, Nayana; Pal, Sourav

doi:10.1063/1.4817943

Cited by 6 publications

(3 citation statements)

References 145 publications

(117 reference statements)

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“…Mk-MRCC, − as developed by Mukherjee and co-workers, is a well-accepted theory in this class. The intermediate Hamiltonian (IH) formulation , can alleviate the problem of loss of convergence to a large extent.…”

Section: Coupled-cluster (Cc) Formalism For Negative Ion Resonancesmentioning

confidence: 99%

Negative Ion Resonance States: The Fock-Space Coupled-Cluster Way

et al. 2020

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The negative ion resonance states, which are electronmolecule metastable compound states, play the most important role in free-electron controlled molecular reactions and low-energy free-electroninduced DNA damage. Their electronic structure is often only poorly described but crucial to an understanding of their reaction dynamics. One of the most important challenges to current electronic structure theory is the computation of negative ion resonance states. As a major step forward, coupled-cluster theories, which are well-known for their ability to produce the best approximate bound state electronic eigen solutions, are upgraded to offer the most accurate and effective approximations for negative ion resonance states. The existing Fock-space coupled-cluster (FSCC) and the equation-ofmotion coupled-cluster (EOM-CC) approaches that compute bound states are redesigned for the direct and simultaneous determination of both the kinetic energy of the free electron at which the electron-molecule compound states are resonantly formed and the corresponding autodetachment decay rate of the electron from the metastable compound state. This Feature Article reviews the computation of negative ion resonances using the FSCC approach and, in passing, provides the highlights of the equivalent EOM-CC approach.

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Section: Coupled-cluster (Cc) Formalism For Negative Ion Resonancesmentioning

confidence: 99%

Negative Ion Resonance States: The Fock-Space Coupled-Cluster Way

et al. 2020

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“…However, S (1,1) can be determined by putting the intermediate normalization on the selectively chosen eigenvectors, analogous to that in one valence problem. Very recently Pal and co-workers 72 have extended the idea for calculation of properties in (1,1) sector, within the IH framework.…”

Section: P H P H P H P H P H P H M P Hmentioning

confidence: 99%

Intermediate Hamiltonian Fock Space Multireference Coupled Cluster Approach to Core Excitation Spectra

Dutta

Gupta

Vaval

et al. 2014

J. Chem. Theory Comput.

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The Fock space multireference coupled cluster (FSMRCC) method provides an efficient approach for the direct calculation of excitation energies. In intermediate Hamiltonian (IH-FSMRCC) formulation, the method is free from intruder state problems and associated convergence difficulties, even with a large model space. In this paper, we demonstrate that the IH-FSMRCC method with suitably chosen model space can be used for the accurate description of core excitation spectra of molecules, and our results are in excellent agreement with the experimental values. We have investigated the effect of choice of model space on the computed results. Unlike the equation-of-motion (EOM)-based method, the IH-FSMRCC does not require any special technique for convergence and in singles and doubles approximation gives a performance comparable to that of the standard EOMEE-CCSD method, even better in some of the cases.

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“…A Fock‐space coupled cluster (FSCC) theory using such a reference has been well developed for excitation energies and response properties . Although, in principle, the theory provides the excited state wave function, its use in the calculation of transition dipole moment has been scarce, mainly because of the description of the conjugate (left) vector of not just the ground state but also the excited state.…”

Section: Introductionmentioning

confidence: 99%

Electronic transition dipole moment: A semi‐biorthogonal approach within valence universal coupled cluster framework

Bhattacharya

Vaval

Pal

2014

Int J of Quantum Chemistry

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Electronic dipole strengths (square of transition moments) and oscillator strengths are evaluated for various transitions, arising from the ground state to a few valence excited states. Parallel to two other methods of calculating the dipole strength within the Fock‐space multireference coupled cluster framework, a new semi‐biorthogonal approach is formulated and implemented in this article. This semi‐biorthogonal approach can evaluate dipole strengths at a lower computational effort than the biorthogonal approach without compromising on the accuracy. This new method is compared and tested against the previously developed expectation value and biorthogonal approach for various molecular transitions. © 2014 Wiley Periodicals, Inc.

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A Lagrange multiplier approach for excited state properties through intermediate Hamiltonian formulation of Fock space multireference coupled-cluster theory

Cited by 6 publications

References 145 publications

Negative Ion Resonance States: The Fock-Space Coupled-Cluster Way

Negative Ion Resonance States: The Fock-Space Coupled-Cluster Way

Intermediate Hamiltonian Fock Space Multireference Coupled Cluster Approach to Core Excitation Spectra

Electronic transition dipole moment: A semi‐biorthogonal approach within valence universal coupled cluster framework

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