Since the effect of spin-orbit coupling plays an important role in a topological insulator, How to change the spin-orbit coupling strength in VASP
?
1 Answer
How to change the spin-orbit coupling strength in VASP?
Firstly, one can't realize this just by changing the input parameters in the INCAR
for 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 relativistic.F
:
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 vasp_std
.
PS1: The answer is for the vasp.5.4.4.
PS2: You may take a look at this paper about the implementation of spin-orbit coupling in VASP
. Or you may take a look at this post in matter modeling: Regarding spin-orbit coupling on DFT codes.
Hope it helps.
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$\begingroup$ Thacks for your answer. I will try to check it. $\endgroup$– LeiWangApr 5, 2021 at 9:02
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$\begingroup$ Is this legal? I mean, from the physical point of view... $\endgroup$– Camps ♦Apr 5, 2021 at 11:50
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$\begingroup$ @Camps Mathematically meaningful. The SOC effect of real materials is hardly changed. Maybe you can only replace the atoms to realize that. $\endgroup$– JackApr 5, 2021 at 11:58
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$\begingroup$ My concern is that, using that hack, you can fake the results. $\endgroup$– Camps ♦Apr 5, 2021 at 12:11
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$\begingroup$ @Camps I guess the method is generally adopted just to investigate the gradual behavior of SOC. $\endgroup$– JackApr 5, 2021 at 12:17