Efficient predictive
capabilities are essential for the actinide
series since regulatory constraints for radioactive work, associated
costs needed for specialized facilities, and the short half-lives
of many actinides present great challenges in laboratory settings.
Improved predictive accuracy is advantageous for numerous applications
including the optimization and design of separation agents for nuclear
fuel and waste. One limitation of calculations in support of these
applications is that the large variations observed from predictions
obtained with currently available methods can make comparisons across
studies uncertain. Benchmarking currently available computational
methodologies is essential to establish reliable practices across
the community to guarantee an accurate physical description of the
systems studied. To understand the performance of a variety of common
theoretical methods, a systematic analysis of differences observed
in the prediction of structural characteristics, electron withdrawing
effects, and binding energies of [An(NO
3
)]
2+
(with An = Ac to Lr) in gas and aqueous phases is reported. Population
analysis obtained with Mulliken and Löwdin reflect a large
dependence on the level of theory of choice, whereas those obtained
with natural bond orbital show larger consistency across methodologies.
Predicted stability across the actinide series calculated with coupled
cluster with perturbative doubles and triples at the triple ζ
level is equivalent to the one obtained when extrapolated to the complete
basis set limit. The ground state of [Fm(NO
3
)]
2+
and [Md(NO
3
)]
2+
is predicted to have an electronic
structure corresponding to An III state in gas and An IV in aqueous
phase, whereas the ground state of [An(NO
3
)]
2+
(with An = Ac to Es, Lr) presents an electronic structure corresponding
to An IV in the gas and aqueous phase. The compounds studied with
No in gas and aqueous phase present a preferred No III state, and
the Lr compounds did not follow trends predicted for the rest of the
actinide series, as previously observed in studies regarding its unusual
electronic structure relative to its position in the periodic table.
Highly-symmetrical, thorium and uranium octakis-carbene ‘sandwich’ complexes have been prepared by ‘sandwiching’ the An(iv) cations between two anionic macrocyclic tetra-NHC ligands, one with sixteen atoms and the other with eighteen atoms.
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