Prediction of a further irregularity in the electron filling of subshell: Lu^-(Xe)4f¹⁴5d¹6s²6p¹and its relation to the group IIIB anions

Dirac-Hartree-Fock theory (DHF), and density functional theory Hartree-Fock system (DFT-HF) calculations predict that Lu- (Z=71) is stable in the (Xe)4f145d16s26p1 odd-parity electron configuration and is not bound in the commonly assumed (Xe)4f145d26s2 even-parity configuration of Hf0 (Z=72). Combining the results of these methods gives an electron affinity approximately=7+or-4 Hartree. The Hartree-Fock energy dominates the crossover from even to odd parity ground state as Z is lowered from 72 to 71 in this 72 electron system. The relativistic effects, which are inherent to the DHF method, are important in unbinding the even-parity state and have been included perturbatively in the DFT-HF calculations. The very large experimental sd interconfiguration energy of Lu0 is used to support the conclusion that the even-parity configuration is unstable. A comparison of the electron configuration of singly charged (+or-) and neutral Lu with those of the group IIIB elements indicates that Lu is most similar to Y.