[Wien] Spin-orbit computation

[Saeid Jalali]

    An straightforward answer to this question  may be just experience. One can monitor the convergence procedures  during two given approaches to realize why it is recommended to include  gradually the spin-orbit coupling (SOC) to a well previously converged  SCF in the absence of SOC. This answer can satisfy everyone in the case  of observing considerable improvement on the convergence procedure (as  discussed before by Lyudmila).
      However,  to be more curios one can back to the time-independent perturbation  theory. In this theory the perturbed Hamiltonians are diagonalized in  the space of non-perturbed eigenstates.
      If  we take SOC term as perturbed Hamiltonians, then performing an SCF  without SOC generates the scalar-relativistic eigenstates, case.vector.  Now including SOC can be interpreted as a diagonalization of the SOC  term in the generated space of case.vectorup(dn) to generate new  eigenstates of case.vectorso. This will reduce the oscillation and save  the time as well. In the presence of SOC the up and down spins are not  longer independent leading to a non-diagonal matrix and thereby we  encounter a doubled matrix which should be  diagonalized from scratch. 
    

"Atta-fynn, Raymond" <attafynn at uta.edu> wrote:      Dear WIEN users,
   
  It is clearly stated in the manual that to   do Spin-orbit (SO) computation, 
  one has to run a regular   scf calculation, save the results, initialize SO, and  run   
  the SO calculation, that is
   
  (1) runsp_lapw -i 100 -ec   0.00001
  (2) save results
  (3) initso
  (4) runsp_lapw -so -i 100 -ec   0.00001
   
  My question is why run   non-SO  first followed by SO. 
  What is wrong with just initializing SO and   going straight ahead 
  with the SO calculation (that is just   execute steps 3 and 4 and skip step 1).
   
  Thanks
   
  R. Atta-Fynn 
   

     

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Sincerely yours,
S. Jalali.
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Saeid Jalali Asadabadi,
Department of Physics, Faculty of Science,
University of Isfahan (UI), Hezar Gerib Avenue,
81744 Isfahan, Iran.
Phones:
Dep. of Phys.      :+98-0311-793 2435
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E-mail             :s_jalali_a at yahoo.com
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