Equation-of-motion coupled-cluster theory based on the 4-component Dirac–Coulomb(–Gaunt) Hamiltonian. Energies for single electron detachment, attachment, and electronically excited states

Shee, Avijit; Saue, Trond; Visscher, Lucas; Gomes, André Severo Pereira

doi:10.1063/1.5053846

Cited by 79 publications

(85 citation statements)

References 169 publications

(192 reference statements)

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“…In conventional EOM-CC methods typically only singlet excited states are targeted, while triplet excitation energies can be obtained using, for instance, spin-flip, [74] ionization-potential/electron-affinity, [75] and other variants of the EOM formalism. [76][77][78] In this work, however, we only investigated singlet excitations in EOM-CC calculations. We first focus on the lowest-lying 1 D (6s !…”

Section: The Electronic Structure Of the Ytterbium Atommentioning

confidence: 99%

Modeling the electronic structures of the ground and excited states of the ytterbium atom and the ytterbium dimer: A modern quantum chemistry perspective

Tecmer

Boguslawski

Borkowski

et al. 2019

Int J of Quantum Chemistry

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We present a comprehensive theoretical study of the electronic structures of the Yb atom and the Yb 2 molecule, respectively, focusing on their ground and lowest-lying electronically excited states. Our study includes various state-of-the-art quantum chemistry methods such as CCSD, CCSD(T), CASPT2 (including spin-orbit coupling), and EOM-CCSD as well as some recently developed pCCD-based approaches and their extensions to target excited states. Specifically, we scan the lowest-lying potential energy surfaces of the Yb 2 dimer and provide a reliable benchmark set of spectroscopic parameters including optimal bond lengths, vibrational frequencies, potential energy depths, and adiabatic excitation energies. Our in-depth analysis unravels the complex nature of the electronic spectrum of Yb 2 , which is difficult to model accurately by any conventional quantum chemistry method. Finally, we scrutinize the biexcited character of the first 1 Σ + g excited state and its evolution along the potential energy surface. K E Y W O R D S relativistic effects, electron corellation effects, spin-orbit coupling, equation of motion coupled cluster, CASPT2 | INTRODUCTIONThe divalent ytterbium atom has in recent years garnered significant attention thanks to its many uses in cold atom physics. It has a nonmagnetic 1 S 0 ground state and several useful optical transitions: the strong 1 S 0 $ 1 P 1 line can be used for Zeeman slowing, whereas the narrow (181 kHz) intercombination 1 S 0 $ 3 P 1 line can be used to directly laser cool Yb atoms to microkelvin temperatures. [1] Yb has seven stable isotopes: two fermions (171 and 173 with nuclear spins of 1/2 and 5/2, respectively) and five bosons (168, 170, 172, 174, and 176) that lack nuclear spin. The rich isotope structure makes it possible to mass-tune the atomic interactions [2] and facilitates a wide array of possible quantum-degenerate gases. [3][4][5][6] The doubly forbidden 1 S 0 $ 3 P 0 transition lies at the heart of optical atomic clocks [7] that are among the most precise physical instruments known to mankind. For example, an ytterbium clock has recently been demonstrated to enable geopotential measurements with an accuracy below a centimeter. [8] The long-lived 3 P 0 clock states also find use in quantum simulations using Yb atoms. [9] The long-range interactions in the Yb dimer have been probed extensively by high-resolution photoassociation spectroscopy (PAS) [10] near the narrow 1 S 0 $ 3 P 1 intercombination line. The excited 1 S 0 + 3 P 1 (0 + u ) [11,12] state has been probed by single color PAS and provided the van der Waals C 6 coefficient and an improved value of the atomic 3 P 1 lifetime. Two-color PAS of ground state 0 + g vibrational levels [2,13] delivered accurate

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Section: The Electronic Structure Of the Ytterbium Atommentioning

confidence: 99%

Modeling the electronic structures of the ground and excited states of the ytterbium atom and the ytterbium dimer: A modern quantum chemistry perspective

Tecmer

Boguslawski

Borkowski

et al. 2019

Int J of Quantum Chemistry

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“…Considering 2 DC M -CCSD(T) to be the gold standard -it was shown by Shee et al [19] that 2 DC M Hamiltonian yields results which are nearly indistinguishable from the Dirac-Coulomb Hamiltonian -and the fact that there are more experimental data estimating the enthalpy of formation, the PuO 2 molecular system represents an excellent candidate to benchmark relativistic multiref-erence methods with an a posteriori treatment of the spin-orbit coupling (SOC) interaction, namely the stateinteraction-multi-state second-order perturbation theory RASSI-MS-CASPT2 approach, hereafter referred to as SO-CASPT2, which has been used to compute the thermodynamic data of PuO 3 and PuO 2 (OH) 2 . High accuracy is achieved by extrapolating the electronic energies to the complete basis set limit.…”

Section: Introductionmentioning

confidence: 99%

Accurate Predictions of Volatile Plutonium Thermodynamic Properties

et al. 2019

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Having the ability to predict the nature and amounts of plutonium emissions in industrial accidents, such as in solvent fires at PUREX nuclear reprocessing facilities, is a key concern of nuclear safety agencies. In accident conditions and in the presence of oxygen and water vapor, plutonium is expected to form three major volatile species PuO2, PuO3, and PuO2(OH)2, for which the thermodynamic data necessary for predictions (enthalpies of formation and heat capacities) presently shows either large uncertainties or is lacking. In this work we aim to alleviate such shortcomings by obtaining the aforementioned data via relativistic correlated electronic structure calculations employing the Multi-State Complete Active Space with Second-Order Perturbation Theory (MS-CASPT2) with state-interaction RASSI spin-orbit coupling approach, which is able to describe the multireference character of the ground-state wavefunctions of PuO3 and PuO2(OH2). We benchmark this approach by comparing it to relativistic coupled cluster calculations for the ground, ionized and excited states of PuO2. Our results allow us to predict enthalpies of formation ∆ f H − • (298.15 K) of PuO2, PuO3 and PuO2(OH)2 to be (−449.5 ± 8.3) kJ mol −1 , (−553.2 ± 27.3) kJ mol −1 , and (−1012.6 ± 38.0) kJ mol −1 , respectively, which confirm the predominance of plutonium dioxide, but also reveal the existence of plutonium trioxide in gaseous phase under oxidative condition, though the partial pressures of PuO3 and PuO2(OH)2 are nonetheless always rather low under wet atmosphere. Our calculations also permit us to reassess prior results for PuO2, establishing the ground state of the PuO2 molecule is mainly of 5 Σ + g character, as well as to confirm the experimental value for the adiabatic ionization energy of PuO2.

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“…95 Further, we have implemented the open-shell reference four-component EOMCC method and applied to calculate ionization potential of super-heavy atomic and molecular systems using DC Hamiltonian. 98 Recently, Shee et al 99 used Dirac-Coulomb-Gaunt Hamiltonian in their implementation of the EOMCC method.…”

Section: Introductionmentioning

confidence: 99%

Relativistic double-ionization equation-of-motion coupled-cluster method: Application to low-lying doubly ionized states

Pathak

Sasmal

Talukdar

et al. 2020

The Journal of Chemical Physics

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The article deals with the extension of the relativistic double-ionization equation-of-motion coupled-cluster (DI-EOMCC) method [H. Pathak et al. Phys. Rev. A 90, 010501(R) (2014)] for the molecular systems. The Dirac-Coulomb (DC) Hamiltonian with four-component spinors is considered to take care of the relativistic effects. The implemented method is employed to compute a few low-lying doubly ionized states of noble gas atoms (Ar, Kr, Xe, and Rn) and Cl 2 , Br 2 , HBr, and HI. Additionally, we presented results with two intermediate schemes in the four-component relativistic DI-EOMCC framework to understand the role of electron correlation. The computed double ionization spectra for the atomic systems are compared with the values from the non-relativistic DI-EOMCC method with spin-orbit coupling (SOC) [Z. Wang et al. J. Chem. Phys. 142, 144109 (2015)] and the values from the National Institute of Science and Technology (NIST) database. Our atomic results are found to be in good agreement with the NIST values. Further, the obtained results for the molecular systems agree well with the available experimental values.

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Equation-of-motion coupled-cluster theory based on the 4-component Dirac–Coulomb(–Gaunt) Hamiltonian. Energies for single electron detachment, attachment, and electronically excited states

Cited by 79 publications

References 169 publications

Modeling the electronic structures of the ground and excited states of the ytterbium atom and the ytterbium dimer: A modern quantum chemistry perspective

Modeling the electronic structures of the ground and excited states of the ytterbium atom and the ytterbium dimer: A modern quantum chemistry perspective

Accurate Predictions of Volatile Plutonium Thermodynamic Properties

Relativistic double-ionization equation-of-motion coupled-cluster method: Application to low-lying doubly ionized states

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