The fully relativistic effects including the spinorbit coupling
within the pseudopotential scheme can be included in the noncollinear
DFT calculations [12,21,15],
while the inclusion of the spinorbit 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 jdependent pseudopotentials
First, you are requested to generate jdependent pseudopotentials
using ADPACK. For your convenience, the jdependent pseudopotentials
are available for many elements in the database Ver. 2013 [102].
The details how to make the jdependent pseudopotential are found in
the manual of ADPACK.
(2) SCF calculation
If you specify jdependent pseudopotentials in the specification of
'Definition.of.Atomic.Species',
it is possible to include spinorbit
coupling by the following keyword 'scf.SpinOrbit.Coupling':
scf.SpinOrbit.Coupling on # OnOff, default=offThen, the spinorbit coupling can be selfconsistently incorporated within the pseudopotential scheme rather than a perturbation scheme. Due to the spinorbit coupling, and spin components in the two component spinor can directly interact. In order to determine the absolute spin orientation in the noncollinear DFT calculations, you have to include the spinorbit coupling, otherwise the spin orientation is not uniquely determined in real space. As an illustration of spinorbit splitting, we show band structures of a bulk GaAs calculated by the noncollinear DFT without and with spinorbit coupling in Fig. 28, where the input file is 'GaAs.dat' in the directory 'work'. In Fig. 28(b) we can see that there are spinorbit splittings in the band dispersion, while no spinorbit splitting is observed in Fig. 28(a). The spinorbit splittings at two kpoints, and , are listed together with the other calculations and experimental values in Table 4. We see a good agreement in this table.

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