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

Abstract

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.

Remarkably High Stability of Late Actinide Dioxide Cations: Extending Chemistry to Pentavalent Berkelium and Californium

“…[39,40] The aug-ccpVDZ basis set [41,42] was used for Oa nd the aug-cc-pVDZ-PP basis sets [43][44][45][46] with effective core potentials were used for An = Ua nd Pa, and the Stuttgart large core effective core potential [47] and associated basis sets [48,49] for the remaining An. The DFT calculations provided starting geometries for subsequent CCSD(T) calculations.…”

“…The DFT calculations were done with the Gaussian 09 program system. [50] Starting from the DFT optimized geometries, CCSD(T) [51][52][53][54] (coupled cluster theory with single and double excitations and ap erturbative triples correction) geometry optimizations using the 3rd-order Douglas-Kroll-Hess Hamiltonian [55][56][57] were carried out using the aug-cc-pwCVDZ-DK for O [42,58,59] and cc-pwCVDZ-DK3 for An [43,60] basis sets. This is denoted in the text as CCSD(T)/cc-pwCVDZ-DK3/ aug-cc-pwCVDZ-DK.…”

Reactions of Th+ + H2, D2, and HD Studied by Guided Ion Beam Tandem Mass Spectrometry and Quantum Chemical Calculations

“…Thresholds are used to determine the bond dissociation energy (BDE), D 0 (Th + −H), using eq 2 and its isotopic analogues. 70 atomic natural orbital basis sets designed for use with the MWB (ANO-VQZ-MWB) 70 and MDF (ANO-VQZ-MDF) 66 ECPs, and correlation consistent cc-pVTZ-MDF, ccpVQZ-MDF, and cc-pwCVTZ-MDF (which includes core− valence correlation) basis sets 65 with the MDF ECP. Pople 6-311+G(3p), cc-pVTZ, and cc-pVQZ basis sets 67 are also used for H. Additionally, BDEs are calculated using single point energies utilizing the all-electron variants of cc-pVXZ (ccpVXZ-DK3) and cc-pwCVXZ (cc-pwCVXZ-DK3) basis sets (where X = T or Q) and B3LYP/cc-pwCVQZ-MDF/aug-ccpVQZ optimized structures.…”

Gaussian Basis Sets for Lanthanide and Actinide Elements

“…This is currently being mitigated by work in one of the authors' groups whereby the cc-pVnZ-PP basis set family (n=D, T, Q, etc. ), which have been previously developed for both transition metals and post-d, main group elements (see [47] and [48] and references therein), is being extended to the f -block [49]. As in these previous works, the sets are optimized in conjunction with the newest available small-core, energy consistent PPs that were adjusted to atomic energy differences computed at the multiconfigurational Dirac-HartreeFock level of theory together with perturbational estimates of the Breit interaction.…”