Ionization potentials and radii of atoms and ions of element 104 (unnilquadium) and of hafnium (2 +) derived from multiconfiguration Dirac-Fock calculations

Multiconfiguration relativistic Dirac–Fock (MCDF) values have been computed for the first four ionization potentials (IPs) of element 104 (unnilquadium) and of the other group 4 elements (Ti, Zr, and Hf). Factors were calculated that allowed correction of the systematic errors between the MCDF IPs and the experimental IPs. Single ‘‘experimental’’ IPs evaluated in eV (to ±0.1 eV) for element 104 are: [104(0),6.5]; [104(1+),14.8]; [104(2+),23.8]; [104(3+),31.9]. Multiple experimental IPs evaluated in eV for element 104 are: [(0−2+),21.2±0.2]; [(0−3+),45.1±0.2]; [(0−4+),76.8±0.3]. Our MCDF results track 11 of the 12 experimental single IPs studied for group 4 atoms and ions. The exception is Hf(2+). We submit our calculated IP of 22.4±0.2 eV as much more accurate than the value of 23.3 eV derived from experiment.