Route to Chemical Accuracy for Computational Uranium Thermochemistry

Abstract

Benchmark spinor-based relativistic coupled-cluster calculations for the ionization energies of the uranium atom, the uranium monoxide molecule (UO), and the uranium dioxide molecule (UO 2 ) and for the bond dissociation energies of UO and UO 2 are reported. The accuracy of these calculations in the treatments of relativistic, electroncorrelation, and basis-set effects is analyzed. The intrinsic convergence of the computed results and the favorable comparison with the experimental values demonstrate the unique applicability of the spinor representation of quantum-chemical methods to open-shell uranium-containing atomic and molecular species with uranium oxidation states ranging from U(0) to U(V).

Bond Energies of UO+ and UC+: Guided Ion Beam and Quantum Chemical Studies of the Reactions of Uranium Cation with O2 and CO

“…Finally, the FPD value for D 0 (UO) is also in excellent agreement with our chosen literature value of 757±13 kJ/mol (7.85±0.13 eV) and with the value derived from the present result, 745±8 kJ/mol (7.72±0.09 eV). The FPD values for both the D 0 and IE of UO are in good agreement with the recent relativistic CCSD(T) calculations of Zhang and Cheng [122] . Note that to confidently obtain an accuracy of a few kJ/mol as acquired here, CCSDT(Q) calculations are necessary, comparable to transition metal species (see for instance Ref [123]…”

“…The FPD values for both the D 0 and IE of UO are in good agreement with the recent relativistic CCSD(T) calculations of Zhang and Cheng. [122] Note that to confidently obtain an accuracy of a few kJ/mol as acquired here, CCSDT(Q) calculations are necessary, comparable to transition metal species (see for instance Ref. [123] ).…”

Cholesky Decomposition-Based Implementation of Relativistic Two-Component Coupled-Cluster Methods for Medium-Sized Molecules

“…Similar to the case of uranium-containing small molecules, , it is essential to account for the correlation of semicore electrons, i.e., the uranium 5s, 5p, and 5d electrons, when aiming at an accurate estimate for the basis-set-limit value of the electron-correlation contribution to the dissociation energy of UF 6 . The electron-correlation contributions with semicore electrons correlated are 253.5, 246.9, and 242.1 kJ/mol for the cVTZ, cVQZ, and cV∞Z basis sets, respectively.…”

“…To benchmark the accuracy of the CD-based X2CAMF-CCSD­(T) and EOM-CCSD calculations, IEs of U, UO, and UO 2 , bond-dissociation energies ( D e ) of UO and UO 2 , and the first 18 VEEs of UO 2 2+ and UN 2 have been calculated with Cholesky thresholds of 10 –δ (δ = 3, 4, 5, and 6) and compared with the results obtained in corresponding traditional calculations without approximating the two-electron integrals. The reference values for IEs and D e s have been taken from ref . The convergence patterns of the computed IEs and D e s and those for the computed VEEs, as well as the number of Cholesky vectors as a function of the Cholesky threshold, are plotted in Figures – , respectively.…”

DAPD Set of Pd-Containing Diatomic Molecules: Accurate Molecular Properties and the Great Lengths to Obtain Them

“…The stringent requirements for transition metals have contributed to fewer high-quality computational data being obtained in comparison with main-group species, for which well-known large data sets are available. , Nonetheless, efforts have continued to be made in closing this gap (see, for example, refs − ). In recent years, we have produced several thermochemistry data sets of transition-metal species, with values of the quality of ∼CCSDT­(Q) at the complete-basis-set (CBS) limit. , They complement our earlier studies into a different set of transition-metal reactions, as well as investigations of other systems that are challenging to computational chemistry. − …”