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?

enter image description here

  • $\begingroup$ Welcome to our community! $\endgroup$
    – Jack
    Apr 5 '21 at 8:04

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.

  • $\begingroup$ Thacks for your answer. I will try to check it. $\endgroup$
    – LeiWang
    Apr 5 '21 at 9:02
  • $\begingroup$ Is this legal? I mean, from the physical point of view... $\endgroup$
    – Camps
    Apr 5 '21 at 11:50
  • $\begingroup$ @Camps Mathematically meaningful. The SOC effect of real materials is hardly changed. Maybe you can only replace the atoms to realize that. $\endgroup$
    – Jack
    Apr 5 '21 at 11:58
  • $\begingroup$ My concern is that, using that hack, you can fake the results. $\endgroup$
    – Camps
    Apr 5 '21 at 12:11
  • $\begingroup$ @Camps I guess the method is generally adopted just to investigate the gradual behavior of SOC. $\endgroup$
    – Jack
    Apr 5 '21 at 12:17

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.