Since the effect of spin-orbit coupling plays an important role in a topological insulator, How to change the spin-orbit coupling strength in
How to change the spin-orbit coupling strength in VASP?
Firstly, one can't realize this just by changing the input parameters in the
VASP. To tune the strength of spin-orbit coupling in
VASP, you need to modify the source file
vasp_source_code_path/src/relativistic.F and recompile it. For example, if you want to reduce the strength to half you can just multiply
0.5d0 to the $L \cdot S$ term in line 129 of
DO I=0,1 DO J=0,1 DO M =1,2*LL+1 DO MP=1,2*LL+1 DLLMM(LMP+MP-1,LM+M-1,J+2*I+1)=DLLMM(LMP+MP-1,LM+M-1,J+2*I+1)+ & 0.5d0*SUM*LS(M,MP,I+2*J+1,LL) !!!line 129 relativistic.F file END DO END DO END DO END DO
Note that you need to use the recompiled $vasp_ncl$ to run your calculation. As a benchmark, if you multiply
0.0d0 to the $L \cdot S$ term in line 129 of
relativistic.F then you will receive the same result as the result obtained with
PS1: The answer is for the vasp.5.4.4.
Hope it helps.