Scalar-relativistic/spin-free function

Depending on commutation properties, the relativistic corrections E [Ve and E2[Ve may be separated into scalar relativistic (SR) and spin-orbit (SO) terms [77]. When SO terms, in particular those related to ia pVxp), are dropped, the two-component treatment is reverted to an effectively one-component method with a trivial spin-dependence of the wave functions such models are sometimes referred to as scalar relativistic, spin-free, or quasi-relativistic [2]. Such calculations are in many technical aspects very similar to the correspond-... 

To demonstrate the effect of different orders in DKH calculations. Table 16.4 presents results obtained for SnO and CsH (different ansatze for the electronic wave function were employed). As can be seen from the table, all spectroscopic parameters converge fast with increasing DKH order. The accuracy is mostly determined by the quality of the wave-function approximation. Note that DKHn denotes the scalar-relativistic variant, which has also been called the spin-averaged (i.e., the spin-free) DKH approach. Also, the two-electron terms have not been transformed. Since the nuclear charge numbers of Sn and Cs are not very high, these elements are not ultrarelativistic cases. However, also for Au2 it was found that the spectroscopic parameters are already converged with the second-order DKH2 Hamiltonian [1127], which is typical for such valence-shell dominated properties. 

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