Two-Component Spin-orbit Effective Core Potential Calculations with an All-electron Relativistic Program DIRAC

Park, Young Choon; Lim, Ivan S.; Lee, Yoon Sup

doi:10.5012/bkcs.2012.33.3.803

Cited by 27 publications

(20 citation statements)

References 29 publications

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“…Contributions due to spin-orbit coupling, ∆SO, were calculated using completely uncontracted VDZ basis sets with either a 2-component ECP Hamiltonian 45 with the SO parameters included with the Th and U PPs, 15,16 (for Eq. (3a)) or by utilizing the exact two-component (X2C) Hamiltonian, which includes atomic-mean-field 2-electron spin-same-orbit corrections 46-49 (for Eq.…”

Section: Molecularmentioning

confidence: 99%

Correlation consistent basis sets for actinides. I. The Th and U atoms

Peterson

2015

The Journal of Chemical Physics

156

189

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New correlation consistent basis sets based on both pseudopotential (PP) and all-electron Douglas-Kroll-Hess (DKH) Hamiltonians have been developed from double- to quadruple-zeta quality for the actinide atoms thorium and uranium. Sets for valence electron correlation (5f6s6p6d), cc - pV nZ - PP and cc - pV nZ - DK3, as well as outer-core correlation (valence + 5s5p5d), cc - pwCV nZ - PP and cc - pwCV nZ - DK3, are reported (n = D, T, Q). The -PP sets are constructed in conjunction with small-core, 60-electron PPs, while the -DK3 sets utilized the 3rd-order Douglas-Kroll-Hess scalar relativistic Hamiltonian. Both series of basis sets show systematic convergence towards the complete basis set limit, both at the Hartree-Fock and correlated levels of theory, making them amenable to standard basis set extrapolation techniques. To assess the utility of the new basis sets, extensive coupled cluster composite thermochemistry calculations of ThFn (n = 2 - 4), ThO2, and UFn (n = 4 - 6) have been carried out. After accurately accounting for valence and outer-core correlation, spin-orbit coupling, and even Lamb shift effects, the final 298 K atomization enthalpies of ThF4, ThF3, ThF2, and ThO2 are all within their experimental uncertainties. Bond dissociation energies of ThF4 and ThF3, as well as UF6 and UF5, were similarly accurate. The derived enthalpies of formation for these species also showed a very satisfactory agreement with experiment, demonstrating that the new basis sets allow for the use of accurate composite schemes just as in molecular systems composed only of lighter atoms. The differences between the PP and DK3 approaches were found to increase with the change in formal oxidation state on the actinide atom, approaching 5-6 kcal/mol for the atomization enthalpies of ThF4 and ThO2. The DKH3 atomization energy of ThO2 was calculated to be smaller than the DKH2 value by ∼1 kcal/mol.

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Section: Molecularmentioning

confidence: 99%

Correlation consistent basis sets for actinides. I. The Th and U atoms

Peterson

2015

The Journal of Chemical Physics

156

189

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“…The E DK contribution is the difference between DK- and PP-based calculations using wCVTZ basis sets with outer-core electrons correlated of the elements with a PP. Last, E SO is the contribution due to spin–orbit (SO) coupling from elements with pseudopotentials calculated at the two-component CCSD(T) level of theory , using the PP SO parameters − ,, with uncontracted VDZ basis sets (virtual orbital cutoff of 10 au). The term E ZPE is the harmonic zero-point vibrational energy calculated at the CCSD(T)/VTZ level of theory.…”

Section: Computational Detailsmentioning

confidence: 99%

Acidity of M(VI)O₂(OH)₂ for M = Group 6, 16, and U as Central Atoms

et al. 2017

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Gas-phase acidities and aqueous solution pK's are predicted for MO(OH), where the center atom M is a main Group 6, 16, and U atom using the Feller-Peterson-Dixon approach based on coupled cluster CCSD(T) calculations with additional corrections. The gas-phase acidities of the MO(OH) compounds are essentially the same for elements (M) of the same group, 304-310 kcal/mol at 298 K. All of the Group 6 compounds are 5-6 kcal/mol less acidic in the gas phase than HSO. The gas-phase acidity of UO(OH) is calculated to be up to 338.0 kcal/mol, ∼10% less acidic in the gas phase than the other MO(OH) acids. The most acidic molecule in aqueous solution is predicted to be HSO. Overall, for the Group 16 compounds, the pK's increase going down the group, with HPoO predicted to be slightly more acidic than nitric acid. HCrO is the most acidic of the Group 6 transition metal compounds. The aqueous acidities of HMoO and HWO are comparable and about 3 pK units less acidic than HCrO and comparable in acidity to HNO. HUO is not acidic at all in aqueous solution with a pK near 20 pK units and is also not predicted to readily undergo hydrolysis reactions.

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“…The ground state I 2 is well characterized experimentally and has already been chosen in many various studies ,− that can be used to gauge our estimates. Figure shows the ground state energy [relative to the energy at the equilibrium geometry] for I 2 .…”

Section: Numerical Resultsmentioning

confidence: 99%

Four-Component Relativistic State-Specific Multireference Perturbation Theory with a Simplified Treatment of Static Correlation

et al. 2017

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The relativistic multireference (MR) perturbative approach is one of the most successful tools for the description of computationally demanding molecular systems of heavy elements. We present here the ground state dissociation energy surfaces, equilibrium bond lengths, harmonic frequencies, and dissociation energies of Ag, Cu, Au, and I computed using the four-component (4c) relativistic spinors based state-specific MR perturbation theory (SSMRPT) with improved virtual orbital complete active space configuration interaction (IVO-CASCI) functions. The IVO-CASCI method is a simple, robust, useful and lower cost alternative to the complete active space self-consistent field approach for treating quasidegenerate situations. The redeeming features of the resulting method, termed as 4c-IVO-SSMRPT, lies in (i) manifestly size-extensivity, (ii) exemption from intruder problems, (iii) the freedom of convenient multipartitionings of the Hamiltonian, (iv) flexibility of the relaxed and unrelaxed descriptions of the reference coefficients, and (v) manageable cost/accuracy ratio. The present method delivers accurate descriptions of dissociation processes of heavy element systems. Close agreement with reference values has been found for the calculated molecular constants indicating that our 4c-IVOSSMRPT provides a robust and economic protocol for determining the structural properties for the ground state of heavy element molecules with eloquent MR character as it treats correlation and relativity on equal footing.

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Two-Component Spin-orbit Effective Core Potential Calculations with an All-electron Relativistic Program DIRAC

Cited by 27 publications

References 29 publications

Correlation consistent basis sets for actinides. I. The Th and U atoms

Correlation consistent basis sets for actinides. I. The Th and U atoms

Acidity of M(VI)O₂(OH)₂ for M = Group 6, 16, and U as Central Atoms

Four-Component Relativistic State-Specific Multireference Perturbation Theory with a Simplified Treatment of Static Correlation

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Two-Component Spin-orbit Effective Core Potential Calculations with an All-electron Relativistic Program DIRAC

Cited by 27 publications

References 29 publications

Correlation consistent basis sets for actinides. I. The Th and U atoms

Correlation consistent basis sets for actinides. I. The Th and U atoms

Acidity of M(VI)O2(OH)2 for M = Group 6, 16, and U as Central Atoms

Four-Component Relativistic State-Specific Multireference Perturbation Theory with a Simplified Treatment of Static Correlation

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Product

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About

Acidity of M(VI)O₂(OH)₂ for M = Group 6, 16, and U as Central Atoms