lapwso includes spin-orbit (SO) coupling in a second-variational
procedure and computes eigenvalues and eigenvectors (stored in
case.vector) using the scalar-relativistic wavefunctions from
lapw1. For reference see Singh 94 and Novak 97. The SO
coupling must be small, as it is diagonalized in the space of the
scalar relativistic eigenstates. For large spin orbit effects it
might be necessary to include many more eigenstates from lapw1
by increasing EMAX in case.in1 (up to 10 Ry!). It is
considered only within the atomic spheres and thus the results may
depend to some extent on atomic spheres radii. The nonspherical
potential is neglected when calculating
.
In spin-polarized calculations the presence of spin-orbit coupling can split equivalent atoms into non-equivalent ones or at least may lower the symmetry of the system. It is then necessary to consider a larger part of the Brillouin zone and the input for lapw2 should also be modified since the potential has lower symmetry than in the non-relativistic case. The following inputs must be changed:
We recommend to use initso (see Sec.5.2.10) which helps you to setup spinorbit calculations, but in some cases an even more complicated procedure might be necessary.
Note: SO eigenvectors are complex and thus lapw2c must be used in a selfconsistent calculation. Since there are twice as many eigenvalues as in a non-SO calculation the NUME Parameter must be large enough.