Computational Methods: Lanthanides and Actinides

Abstract

First‐principles and semiempirical relativistic quantum chemical methods applicable to molecular systems containing lanthanides and actinides are briefly reviewed. Selected recent applications of some of these methods are discussed.

Spectroscopy and Structure of the Simplest Actinide Bonds

“…From the perspective of fundamental scientific significance, studies of small actinide-containing molecules provide opportunities to evaluate and advance relativistic quantum chemistry models. − Central issues for the actinides concern the participation of the 5f orbitals in chemical bonding, and the unique materials properties that result from the partially filled 5f shell (e.g., superconductivity, heavy-Fermion behavior and single-molecule magnets). Comparisons between the lanthanides and the actinides are complicated by substantial differences in the radial distributions of the 4f and 5f orbitals.…”

Segmented Contracted Douglas–Kroll–Hess Adapted Basis Sets for Lanthanides

“…The open 4f shell causes various difficulties in calculations on lanthanide systems, e.g., large differential relativistic effects usually destabilizing states with high 4f occupation and large counteracting correlation effects stabilizing states with high 4f occupation have to be dealt with. 48,49 Such problems become relevant, e.g., for the calculation of the LnX 3 atomization energies, since in these molecules according to the ionic charge distribution Ln 3+ (X À ) 3 the Ln 3+ centers have a 4f n configuration (n = 0À14 for LaÀLu), whereas in the ground states of the neutral PrÀEu and TbÀYb atoms one has a 4f n+1 6s 2 configuration. 50 Thus, only for La, Ce, Gd, and Lu, where the neutral atoms have a 4f n 5d 1 6s 2 configuration, may one expect a rough cancellation of differential relativistic and correlation effects in the calculation of the atomization energies.…”

Theoretical Study of Bond Distances and Dissociation Energies of Actinide Oxides AnO and AnO2

“…In contrast, theoretical studies on late actinide compounds are very rare, in spite of the theoretical tools available from the mid 1990s. , The tools include both all electron basis sets, such as used in the Amsterdam Density Functional package, and relativistic small-core pseudopotentials with appropriate valence basis sets . The pseudopotentials, extended recently with larger valence basis sets, , have been used to predict the bond lengths, binding energies, and vibrational constants of LrH, LrO, and LrF …”