Relativistic corrections to carbon atom energy levels and their relation to the singlet-triplet splitting in methylene

First results of experimental and theoretical investigations on sextet states of doubly-excited five-electron ions

“…The sextet states couple to maximum spin quantum number S = 5/2, and no different parents are involved in the coupling. Following the rules of Wood and Pyper [12], we therefore do not expect that any extra energies like those described by Huang [13] contribute to our case. Nevertheless we ascertained that in a non-relativistic MCDF calculation (c = 10 1 0 a.u.)…”

Correlation and Relativistic Effects in Spin-Orbit Splitting

“…Nevertheless they are expected to converge to the same nonrelativistic limit, when the fine-structure constant is set equal to zero. In the relativistic SCF procedure, however, as was pointed out by Wood and Pyper, 15 when a configuration has more than one parent core state-such as the (2/> 4 ) 3 P, 1 D, and X S core states of the F-like ions-the two radial functions 2p 3/2 and 2p 1/2 do not converge to the same nonrelativistic limit unless they are forced to do so through additional constraints. When the core states are not unique, a singly excited configuration, such as 2£ 4 3/>, can interact 16 with the groundstate configuration 2/> 5 .…”

The influence of improved dipole-quadrupole dispersion coefficients on the predicted cohesion of ionic oxides

“…For a free Mg2+ ion, the expectation values in (3.2) were evaluated from the numerical Hartree-Fock wavefunction computed using the Oxford atomic Dirac-Fock programme [40] with an artificially large value for the velocity of light. For closed shell systems such computations reproduce exactly [41,42] the results of conventional non-relativistic calculations. The corresponding expectation values for the in-crystal 0'ion were evaluated from an ion wavefunction computed by including in the Dirac-Fock programme the currently most reliable model, the OEMFs model (14,181, for the important interaction between each anion electron and the in-crystal environment.…”