Lanthanide Diatomics and Lanthanide Contractions

Abstract

first-order perturbations including S-O couplings are accounted for. The calculated molecular constants are in reasonable agreement with the experimental ones. The calculated lanthanide contractions of the three series, i.e. R(La-X) -R(Lu-X), are quite different, 0.19 Á (0.19 Á) for LnH, 0.10 Á (0.11 Á) for LnF, and only 0.05 Á (0.04 Á) for LnO.There is good agreement between the calculated values and the experimental ones (values in parentheses). This astonishing variation has two origins, a monoatomic and a diatomic one, which are related to each (DW), spin-orbit (SO), and so-called indirect core effects (DVC). The cores are treated at the Dirac-Fock-Slater level.LnH, LnF, and LnO have been calculated in their ground configurations. In general, the lanthanides are trivalent;27 i.e., the valence configuration is f with N = 0,7, and 14 for La, Gd, and Lu, respectively. But for Yb (N = 13) also the divalent state is common, with occupied f-v+1=14 shell. The superconfigurations of the ground states in general are: (4 ) 2 2 for LnH, (4 ) 2 2 2 3 4 for LnF and (4 ) 2 2 , 4 for LnO.However, there are exceptions. Concerning the Yb compounds, the ground configurations are (4f14)a2a1 for YbH, (4 ,4) 2 2 4 for YbF, and (4 14) 2 2 2 4 for YbO. The significant (4 3) 2 2 1 4 ' + admixture in the YbO ground state12 has been neglected here except where explicitly noted. Another exception is LaH: 4 ° 2 2 represents one of the low-lying excited states.

High-Resolution Laser Spectroscopy of YbCl: The A2Π–X2Σ+ Transition

“…However, both ab initio calculations (7) and measurement of the dipole moment (5) have shown that the orbital is a 6s ϳ 6p hybrid polarized away from the fluorine. The ab initio calculations also indicate that the 6p contribution to the ground state orbital is 15%, a result that is supported by very good agreement between the calculated and experimental dipole moments (5,(7)(8)(9). Although there have been no similar experiments or calculations for YbCl, it is expected that the ground state configuration should be very similar to that of YbF.…”

Molecular relativistic calculations of the electric field gradients at the nuclei in the hydrogen halides

“…We obtain at the relativistic MP2 level lanthanide contractions of 0.12, 0.12, and 0.19 Å for the monohydrides, monofluorides, and trihydrides, respectively. The corresponding values for the actinides are 0.20, 0.15, and 0.28 Å. Ligand effects of this type have been observed and discussed in previous studies 2,10 and form the subject of this section. We have performed Mulliken population analysis at the DHF level of the molecular species studied in this work.…”

“…The structure of the lanthanum and lutetium monohydrides, monofluorides, and monoxides were determined by nonrelativistic and quasirelativistic density functional theory ͑DFT͒ by Wang and Schwarz 10 and in high quality correlated pseudopotential calculations by Küchle et al 2 New estimates for the molecular lanthanide contraction were obtained together with an estimate of the influence of relativity. In Ref.…”

“…Valence electrons are treated in a nonrelativistic formalism where these electrons are moving in the effective potential of the frozen core. The pseudopotential comprises the (46ϩn) electron ͓Kr͔4d 10 4 f n -core where nϭ0 for lanthanum and nϭ14 for lutetium and the actinides. Especially for lutetium the frozen core is rather large since the 14 valence 4 f orbitals are included in the pseudopotential.…”

Quasirelativistic energy-consistent 5f-in-core pseudopotentials for trivalent actinide elements

“…3.1.1). The reason for this minor actinide contraction is that the An-F bond is more 'rigid' than the An-O coordination interaction in the water complexes [15,29]. This can be seen from the bond energies which are up to 1.96 eV larger in the case of AnF 3 (cf.…”