Study of Actinides by Relativistic Coupled Cluster Methods

Mechanism and Energetics of the Hydrolysis of Th+To Form Th(OD)3+: Guided Ion Beam and Theoretical Studies of ThO+, ThO2+, and OThOD+Reacting with D2O

“…The ground state of ThO + is 2 Σ + , as identified experimentally using pulsed field ionization-zero kinetic energy photoelectron spectroscopy. 46 This state has a (1σ) 2 (1π) 4 (2σ) 1 valence electron configuration, where the 1σ and 1π orbitals are bonding orbitals formed between O (2p) and Th + (6d) orbitals and the 2σ nonbonding orbital is primarily the Th + (7s) orbital, as shown in Figure 7. Here, we calculate a bond length of 1.807 Å at the B3LYP/cc-pVQZ level, which matches the experimental bond length of 1.807, 46 as well as the bond lengths of 1.808, 1.809, and 1.808 Å calculated by Cox et al, 47 Zhou and Schlegel (ZS), 48 and Mazzone et al (MMRS), 49 respectively.…”

“…3 For the radioactive elements, theoretical calculations may provide a safe and cost-effective alternative to experimental research; however, accurate quantum chemical calculations on actinide species are problematic because of the need to implement relativistic and correlation effects associated with the large number of electrons, further complicated by the close energetic proximity of many electronic states involving the 5f, 6d, 6p, and 7s orbitals. 4 The challenges of these calculations are further exacerbated by a shortage of accurate information on actinide molecules, which makes validation of the approximations employed in the theoretical models difficult. Reliable fundamental experimental benchmarks are necessary in order to investigate potential basis sets and theoretical models.…”

Relativistic Fock Space Coupled Cluster Method for Many-Electron Systems: Non-Perturbative Account for Connected Triple Excitations

“…During recent decades the relativistic Fock Space CC approach in both effective and intermediate Hamiltonian formulations proved its efficiency and high accuracy in challenging calculations of heavy atomic and molecular systems with dense spectra, especially in cases when both d and f atomic orbitals become valence (see also recent reviews [26,29,36]). In the non-relativistic realm the pilot implementation of the FS-CC method accounting for triple excitations and allowing the treatment of up to six valence electrons sectors was pioneered by Hughes and Kaldor in earlier 1990s; they reported calculations of electronic states of light atoms in rather modest basis sets [37][38][39].…”

Considering Density Functional Approaches for Actinide Species: The An66 Molecule Set

“…In addressing actinide species, computational chemistry provides a vital route toward describing their thermochemistry, in part, due to the inherent difficulties of experimental work with such compounds . However, computational methods have their own challenges.…”