Complex-scaled equation-of-motion coupled-cluster method with single and double substitutions for autoionizing excited states: Theory, implementation, and examples

Bravaya, Ksenia B.; Zuev, Dmitry; Epifanovsky, Evgeny; Krylov, Anna I.

doi:10.1063/1.4795750

Cited by 71 publications

(88 citation statements)

References 79 publications

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“…By using complex scaling and complex absorbing potential techniques, we extended these powerful methods to describe autoionising states, such as transient anions, highly excited electronic states, and core-ionised species [183][184][185]. In addition, users can employ stabilisation techniques using charged sphere and scaled atomic charges options [186].…”

Section: Coupled Cluster Methodsmentioning

confidence: 99%

Advances in molecular quantum chemistry contained in the Q-Chem 4 program package

Shao¹,

Gan²,

Epifanovsky³

et al. 2014

Molecular Physics

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A summary of the technical advances that are incorporated in the fourth major release of the Q-Chem quantum chemistry program is provided, covering approximately the last seven years. These include developments in density functional theory methods and algorithms, nuclear magnetic resonance (NMR) property evaluation, coupled cluster and perturbation theories, methods for electronically excited and openshell species, tools for treating extended environments, algorithms for walking on potential surfaces, analysis tools, energy and electron transfer modelling, parallel computing capabilities, and graphical user interfaces. In addition, a selection of example case studies that illustrate these capabilities is given. These include extensive benchmarks of the comparative accuracy of modern density functionals for bonded and non-bonded interactions, tests of attenuated second order Møller-Plesset (MP2) methods for intermolecular interactions, a variety of parallel performance benchmarks, and tests of the accuracy of implicit solvation models. Some specific chemical examples include calculations on the strongly correlated Cr 2 dimer, exploring zeolitecatalysed ethane dehydrogenation, energy decomposition analysis of a charged ter-molecular complex arising from glycerol photoionisation, and natural transition orbitals for a Frenkel exciton state in a nine-unit model of a self-assembling nanotube.Keywords quantum chemistry, software, electronic structure theory, density functional theory, electron correlation, computational modelling, Q-Chem Disciplines Chemistry CommentsThis article is from Molecular Physics: An International Journal at the Interface Between Chemistry and Physics 113 (2015): 184, doi:10.1080/00268976.2014. RightsWorks produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted. Authors 185A summary of the technical advances that are incorporated in the fourth major release of the Q-CHEM quantum chemistry program is provided, covering approximately the last seven years. These include developments in density functional theory methods and algorithms, nuclear magnetic resonance (NMR) property evaluation, coupled cluster and perturbation theories, methods for electronically excited and open-shell species, tools for treating extended environments, algorithms for walking on potential surfaces, analysis tools, energy and electron transfer modelling, parallel computing capabilities, and graphical user interfaces. In addition, a selection of example case studies that illustrate these capabilities is given. These include extensive benchmarks of the comparative accuracy of modern density functionals for bonded and non-bonded interactions, tests of attenuated second order Møller-Plesset (MP2) methods for intermolecular interactions, a variety of parallel performance benchmarks, and tests of the accuracy of implicit solvation models. Some specific chemical examples include calculations on the strongly corre...

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Section: Coupled Cluster Methodsmentioning

confidence: 99%

Advances in molecular quantum chemistry contained in the Q-Chem 4 program package

Shao¹,

Gan²,

Epifanovsky³

et al. 2014

Molecular Physics

Self Cite

2,709

2,077

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“…(6) are square integrable. This feature makes it possible to use bound-state methods to solve (6), including configuration interaction [14,15], Faddeev and Faddeev-Yakubovsky [39,40], and the coupled cluster method [41]. Because the resonant states are square integrable, they can be normalized to one.…”

Section: B Complex-scaling Methodsmentioning

confidence: 99%

Nuclear three-body problem in the complex energy plane: Complex-scaling Slater method

et al. 2014

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Background:The physics of open quantum systems is an interdisciplinary area of research. The nuclear "openness" manifests itself through the presence of the many-body continuum representing various decay, scattering, and reaction channels. As the radioactive nuclear beam experimentation extends the known nuclear landscape toward the particle drip lines, the coupling to the continuum space becomes exceedingly more important. Of particular interest are weakly bound and unbound nuclear states appearing around particle thresholds. Theories of such nuclei must take into account their open quantum nature. Purpose:To describe open quantum systems, we introduce a complex-scaling (CS) approach in the Slater basis. We benchmark it with the complex-energy Gamow shell model (GSM) by studying energies and wave functions of the bound and unbound states of the two-neutron halo nucleus 6 He viewed as an α + n + n cluster system. Methods: Both CS and GSM approaches are applied to a translationally invariant Hamiltonian with the two-body interaction approximated by the finite-range central Minnesota force. In the CS approach, we use the Slater basis, which exhibits the correct asymptotic behavior at large distances. To extract particle densities from the back-rotated CS solutions, we apply the Tikhonov regularization procedure, which minimizes the ultraviolet numerical noise. Results: We show that the CS-Slater method is both accurate and efficient. Its equivalence to the GSM approach has been demonstrated numerically for both energies and wave functions of 6 He. One important technical aspect of our calculation was to fully retrieve the correct asymptotic behavior of a resonance state from the complex-scaled (square-integrable) wave function. While standard applications of the inverse complex transformation to the complex-rotated solution provide unstable results, the stabilization method fully reproduces the GSM benchmark. We also propose a method to determine the smoothing parameter of the Tikhonov regularization. Conclusions:The combined suite of CS-Slater and GSM techniques has many attractive features when applied to nuclear problems involving weakly bound and unbound states. While both methods can describe energies, total widths, and wave functions of nuclear states, the CS-Slater method-if it can be applied-can provide additional information about partial energy widths associated with individual thresholds.

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“…4,[18][19][20][21] The EOM-CC formalism [22][23][24][25][26][27] allows to treat electronically excited 24 (EOM-EE), ionized 28 (EOM-IP), and electron-attached 29 (EOM-EA) states as eigenfunctions of the same effective Hamiltonian, which is crucial for electronic resonances because it enables a consistent description of a resonance relative to the ionization and detachment continua. 30 Furthermore, EOM-CC treats states with different character on an equal footing and by including higher excitations in the ansatz for the wave function, the description can be systematically improved up to the full configuration interaction limit.…”

Section: Introductionmentioning

confidence: 99%

Non-iterative triple excitations in equation-of-motion coupled-cluster theory for electron attachment with applications to bound and temporary anions

Jagau

2018

The Journal of Chemical Physics

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The impact of residual electron correlation beyond the equation-of-motion coupledcluster singles and doubles approximation (EOM-CCSD) on positions and widths of electronic resonances is investigated. To establish a method that accomplishes this task in an economical manner, several approaches proposed for the approximate treatment of triples excitations are reviewed with respect to their performance in the electron attachment (EA) variant of EOM-CC theory.The recently introduced EOM-CCSD(T)(a)* method, which includes non-iterative corrections to the reference and the target states, reliably reproduces vertical attachment energies from EOM-EA-CC calculations with singles, doubles, and full triples excitations in contrast to schemes in which non-iterative corrections are applied only to the target states.

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Complex-scaled equation-of-motion coupled-cluster method with single and double substitutions for autoionizing excited states: Theory, implementation, and examples

Cited by 71 publications

References 79 publications

Advances in molecular quantum chemistry contained in the Q-Chem 4 program package

Advances in molecular quantum chemistry contained in the Q-Chem 4 program package

Nuclear three-body problem in the complex energy plane: Complex-scaling Slater method

Non-iterative triple excitations in equation-of-motion coupled-cluster theory for electron attachment with applications to bound and temporary anions

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