[Wien] Q: charge lost in SO calculation depending on LAPW / APW+lo

[Torsten Andersen]

Dear Dr. Zijlstra,

one suggestion on its cause:

The spin-orbit interaction (s.o.c.) is only implemented inside the 
muffin-tins. You can test the influence of this by maximizing the size 
of the muffin-tins and see if the loss gets smaller.

Also, it (s.o.c.) is implemented in second variation, so you need to 
include the spin-orbit in the whole SCF cycle in order to get reliable 
results. I am not sure that second variation is bulletproof, but usually 
it works.

Best regards,
Torsten Andersen.

Eeuwe Sieds Zijlstra wrote:
> Dear all,
> 
> For bismuth (Bi) I found the following behavior, which I do not understand:
> 
> When 6s states were described by LAPW's and 6p states by APW+lo's
> and when the spin-orbit (SO) interaction was included using a relativistic 
> local p1/2 orbital, 0.33 electrons were lost as can be seen from the 
> following output of MIXER:
> 
> :NEC01: NUCLEAR AND ELECTRONIC CHARGE   83.00000  82.67338   1.00395
> 
> This charge disappears from the p channel as can be seen when QTL is compared 
> for the above case and a case where the 6s states are also described by 
> APW+lo's:
> 
> :QTL001: 1.2922 1.3993 9.8302 0.0642 ....  (above case)
> :QTL001: 1.2631 1.7246 9.8203 0.0643 .... (when 6s is described by APW+lo's)
> 
> No charge was lost when 6s was described by APW+lo's, when 6s and 6p were both 
> described by LAPW 's (but this calculation is unstable, so I did just one 
> iteration), or when no p1/2 orbital was included. 
> 
> I checked that there are no linear dependencies in the second-variational 
> secular equation (the overlap matrix is positive definite) and that this 
> behavior does not depend on Emax or the choice of basis for the d states, 
> i.e., APW+lo or LAPW. There were no QTL-B warnings or other warnings that I 
> am aware of.
> 
> When no p1/2 orbital orbital was included, the total energy was insensitive to 
> whether LAPW or APW+lo was used for 6s and 6p, so in principle these choices 
> form an equally good basis for LAPW1
> 
> I found this behavior for both the A7 structure (with 2 atoms per unit cell) 
> and for simple cubic Bi [space group Pm-3m (number 221), a = 6.18 Bohr,
> Gamma point only with temperature smearing, Eval=0.001 Ry]. The above data are 
> for the latter calculation, which is simpler. For this calculation my files 
> case.in1 and case.inso are:
> 
> ********* case.in1 *************
> WFFIL        (WFPRI, SUPWF)
>   7.00       10    4 (R-MT*K-MAX; MAX L IN WF, V-NMT
>  .07680   4   0      global e-param with N other choices, napw
>  0   -0.364     0.010 CONT 0
>  1    0.205     0.000 CONT 1
>  2   -1.273     0.010 CONT 0
>  2    0.113     0.000 CONT 0
> K-VECTORS FROM UNIT:4   -4.0       0.9      emin/emax window
> ********** end of case.in1 ************
> 
> ********* case.inso ***********
> WFFIL
>  4  4  0                      llmax,ipr,kpot
>  -10.0000   0.90000           emin,emax (output energy window)
>    0.  0.  1.                 direction of magnetization (lattice vectors)
>   1                           number of atoms for which RLO is added
>  1  0.205  0.000  CONT
>  0 0 0 0 0             number of atoms for which SO is switch off;atoms
> ********** end of case.inso ************
> 
> Finally, I checked that this same behavior occured both with the precompiled 
> WIEN2k package and when I compiled WIEN2k with the Portland Group compiler 
> pgf90, with and without optimization.
> 
> My question is, whether anyone has had similar problems? Whether somebody 
> could comment on its cause? I would really like to know, whether there is a 
> bug in the program or whether there is some criterium according to which I 
> can choose my basis set in one way but not in another way and of which I am 
> not aware.
> 
> I hope that this question is not too hard. 
> Any help would of course be greatly appreciated! 
> 
> 
> Sincerely,
> 
> Eeuwe Sieds Zijlstra
> Theoretical Physics
> University Kassel
> Germany
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
> 

-- 
Dr. Torsten Andersen        TA-web: http://deep.at/myspace/
AG Hübner, Department of Physics, Kaiserslautern University
http://cmt.physik.uni-kl.de    http://www.physik.uni-kl.de/