Electronic structure of f(1) actinide complexes. Part 3 of 1 . Quasirelativistic density functional calculations of the optical transition energies of PaX62- (X=F, Cl, Br, I)

The four f→f transition energies of the single 5f-based electron of PaX62− (X=F, Cl, Br, I) have been calculated using quasi-relativistic local density functional theory. Excellent agreement (<200 cm−1) between theory and experiment is obtained for PaCl62−, PaBr62− and PaI62− by variation of the value of α in the Xα exchange-only functional. In contrast, more sophisticated calculational methods including non-local corrections fail to reproduce the experiments well. The PaF62− results are less impressive (up to 1000 cm−1 discrepancy), possibly due to non-aufbau orbital occupations for certain values of α. The values of α employed lie in the range 0.79–0.85, somewhat higher than the most widely used value of 0.7. The theoretical basis for using such values is discussed.