EOM-CC guide to Fock-space travel: the C2 edition

Gulania, Sahil; Jagau, Thomas-C.; Krylov, Anna I.

doi:10.1039/c8fd00185e

Cited by 22 publications

(29 citation statements)

References 84 publications

(24 reference statements)

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“…The 1D xenon model is solved using two different forms of CAPs: SES‐CAP, which is associated with smooth exterior scaling transformations, and the quadratic CAP, which is implemented within quantum chemistry packages for calculation of autoionization resonances . Our study suggests that the SES‐CAP is more appropriate for calculation of Stark resonances, while the quadratic CAP is less accurate.…”

Section: Discussionmentioning

confidence: 99%

“…The results obtained by using the SES‐CAP are compared with the results obtained by the quadratic CAP. The quadratic CAP is implemented within the quantum chemistry packages and is commonly used for calculation of field‐free molecular resonances . To the best of our knowledge, the first ab‐initio many‐electron study using a quadratic CAP is presented in ref.…”

Section: Introductionmentioning

confidence: 99%

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Complex absorbing potentials for stark resonances

Ben‐Asher

Moiseyev

2019

Int J of Quantum Chemistry

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In this work, we study the problem in calculation of Stark resonances by using complex absorbing potentials (CAPs), and its solutions. The motivation of using CAPs for calculating Stark resonances stems from the fact that CAPs can be easily inserted to a large variety of available codes for calculating the electronic structure of molecules and atoms. Our conclusion is that the appropriate CAPs for studying ac/dc Stark resonances are those that are associated with smooth-exterior-scaling (SES) transformations, which rotate the spatial contour of integration into the complex plane. The performance of SES-CAPs vs standard commonly used CAPs in different types of basis sets is investigated.complex absorbing potential, complex energy, resonances, stark effect

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Complex absorbing potentials for stark resonances

Ben‐Asher

Moiseyev

2019

Int J of Quantum Chemistry

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“…All calculations were performed using the Q-Chem electronic structure program 73,74 2 ) closed-shell reference. The dianionic reference is well-behaved (at least, up to the aug-cc-pVTZ basis) 75 and have been used to describe the electronic structure of C 2 , C − 2 , and C 2− 2 .…”

Section: A Computational Detailsmentioning

confidence: 99%

Dissociative Electron Attachment in C2H via Electronic Resonances

Gulania¹,

Krylov²

2021

Preprint

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<div> <div> <div> <div> Investigation of microwave-activated CH4/H2 plasma used in chemical vapor deposition of diamond revealed the presence of electronically excited C2-(B2Σu+). Using high-level electronic structure methods, we investigate electronic structure of C2H- and suggest possible routes for formation of C2- in the ground (X2Σg+) and excited (B2Σu+) states via electronic resonances. To describe electronically meta-stable states, we employ the equation-of-motion coupled-cluster method augmented by the complex absorbing potential. The resonance wave-functions are analyzed using natural transition orbitals. We identified several resonances in C2H-, including the state that may lead to C2-(B2Σu+). </div> </div> </div> </div>

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“…By truncating the cluster operatorT after single and double excitations and adding perturbative triples, we arrive at the CCSD(T) method, which is recognized as the 'gold standard' for singlereference calculations due to its highly accurate and reliable results [6,7]. To some extent, single-reference CC approaches like the linear response CC (LR-CC) theory [8] and EOMCC [9][10][11][12] (which has specialized variants such as spin-flip (SF) [13], ionization potential (IP) [14,15], double ionization potential (DIP) [16], electron attachment (EA) [17,18], and similaritytransformed STEOM [19][20][21]) can describe states that otherwise would require a multireference method [22].…”

Section: Introductionmentioning

confidence: 99%

A perturbative approach to multireference equation-of-motion coupled cluster

2021

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We introduce a variant of the multireference equation-of-motion coupled-cluster (MR-EOMCC) method where the amplitudes used for the similarity transformations are estimated from perturbation theory. Consequently, the new variant retains the many-body formalism, a reliance on at most two-body densities, and the state-universal character. As a non-iterative variant, computational costs are reduced, and no convergence difficulties with near-singular amplitudes can arise. Its performance was evaluated on several test sets covering transition metal atoms, small diatomics, and organic molecules against (near-)full CI quality reference data. We further highlight its efficacy on the weakly avoided crossing of LiF and place MR-EOMCC and the new variant into context with linear response theory. The accuracy of the variant was found to be at least on par with expectations for multireference perturbation theories, judging by the NEVPT2 method. The variant can be especially useful in multistate situations where the high accuracy of the iterative MR-EOMCC method is not required.

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EOM-CC guide to Fock-space travel: the C₂ edition

Abstract: Electronic structure calculations for C2, C2−, and C22− using the CC/EOM-CC family of methods. Results illustrate that EOM-CCSD provides an attractive alternative to MR approaches.

Cited by 22 publications

References 84 publications

Complex absorbing potentials for stark resonances

Complex absorbing potentials for stark resonances

Dissociative Electron Attachment in C2H via Electronic Resonances

A perturbative approach to multireference equation-of-motion coupled cluster

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