The fully relativistic effects including the spin-orbit coupling
within the pseudopotential scheme can be included in the non-collinear
DFT calculations [12,32,16],
while the inclusion of the spin-orbit coupling is not supported in the collinear
DFT calculation. The inclusion of fully relativistic effects is made
by the following two steps:
(1) Making of j-dependent pseudopotentials
First, you are requested to generate j-dependent pseudopotentials using ADPACK. For your convenience, the j-dependent pseudopotentials are available for many elements in the database Ver. 2019 . The details how to make the j-dependent pseudopotential are found in the manual of ADPACK.
(2) SCF calculation
If you specify j-dependent pseudopotentials in the specification of 'Definition.of.Atomic.Species', it is possible to include spin-orbit coupling by the following keyword 'scf.SpinOrbit.Coupling':
scf.SpinOrbit.Coupling on # On|Off, default=offThen, the spin-orbit coupling can be self-consistently incorporated within the pseudopotential scheme rather than a perturbation scheme. Due to the spin-orbit coupling, and spin components in the two component spinor can directly interact. In order to determine the absolute spin orientation in the non-collinear DFT calculations, you have to include the spin-orbit coupling, otherwise the spin orientation is not uniquely determined in real space. As an illustration of spin-orbit splitting, we show band structures of a bulk GaAs calculated by the non-collinear DFT without and with spin-orbit coupling in Fig. 33, where the input file is 'GaAs.dat' in the directory 'work'. In Fig. 33(b) we can see that there are spin-orbit splittings in the band dispersion, while no spin-orbit splitting is observed in Fig. 33(a). The spin-orbit splittings at two k-points, and , are listed together with the other calculations and experimental values in Table 5. We see a good agreement in this table.