[Wien] Question on EFG and eigenvectors and sugestion for the output

[Florent Boucher]

Dear Peter and wien users,
I have a small question (may be a stupid one) but I have difficulties to 
find an answer ...
Concerning the calculation of the EFG in WIEN2k, we have access to the 
eigenvalues of the EFG tensor and to the eigenvectors.
The EFG is a trace less tensor and, using the convention |Vzz| >= |Vyy| 
 >= |Vxx|, we can obtain the quadrupolar parameter Cq = eQVzz/h
with the sign of Cq.
(I hope for the moment I am right ).
Now what about the eigenvectors or principle axis of the tensor.
Is the direction of the  principle axis defined without ambiguity ?
For instance, if I have an atom on a site with a local symmetry -1. I 
was assuming that the principle axis of the EFG tensor can be either in 
one direction or the opposite ?
Am I true ?
If not, why ?

Suggestion for the output of lapw0.
Can we add in the output0 and scf0 the calculation of Cq.
I suggest to add those two lines in efg.f

>             WRITE(6,1340)   
> jatom,VZZ                                         
>             WRITE(6,1341)   V20,V20SRF                                  
>             WRITE(6,1342)   V22,V22SRF                                  
>             WRITE(6,1343)   V22M,V22MSR                                  
>             WRITE(6,1344)   V21,V21SRF                                  
>             WRITE(6,1345)   V21M,V21MSR                                 
>             WRITE(6,1350)   qmat(1,1),qmat(1,2),qmat(1,3),TENS(1),0.,0.
>             WRITE(6,1350)   qmat(2,1),qmat(2,2),qmat(2,3),0.,TENS(2),0.
>             WRITE(6,1350)   qmat(3,1),qmat(3,2),qmat(3,3),0.,0.,TENS(3)
>             WRITE(6,1355)   ((eivec(i,j),j=1,3),i=1,3),jatom,winkel
>             WRITE(6,1356)   jatom,VZZ*24.177d0                        
> <-----                    
>             WRITE(6,1360)   
> jatom,ETA                                         
>  1355 FORMAT(/,9X,'MAIN DIRECTIONS OF THE EFG ',3F8.4,/,36X,3F8.4,/ &
>       ,36X,3F8.4,/, &
>       ':ANG',i3.3,':',1X,'ANGLE WITH OLD X-AXIS =    ',f8.1)
>  1356 FORMAT(/,':CQ_',i3.3,':',1X, 'QUADRUPOLAR PARAMETER =',F12.5,' 
> MHz IF Q IS EQUAL TO 1b (10-28m^2)')   <-----    
>  1360 FORMAT(/,':ETA',i3.3,':',24X,'ASYMM. ETA =',F12.5,//)
and also in lapw0.F

>         IF(logefg(jatom)) THEN
>            WRITE(21,1340)  jatom,efgb(jatom)%vzz
>            WRITE(21,1341)  efgb(jatom)%V20,efgb(jatom)%V20SRF
>            WRITE(21,1342)  efgb(jatom)%V22,efgb(jatom)%V22SRF
>            WRITE(21,1343)  efgb(jatom)%V22M,efgb(jatom)%V22MSR
>            WRITE(21,1344)  efgb(jatom)%V21,efgb(jatom)%V21SRF
>            WRITE(21,1345)  efgb(jatom)%V21M,efgb(jatom)%V21MSR
>            WRITE(21,1350)  efgb(jatom)%qmat(1,1),efgb(jatom)%qmat(1,2), &
>                 efgb(jatom)%qmat(1,3),efgb(jatom)%TENS(1),0.,0.
>            WRITE(21,1350)   efgb(jatom)%qmat(2,1),efgb(jatom)%qmat(2,2), &
>                 efgb(jatom)%qmat(2,3),0.,efgb(jatom)%TENS(2),0.
>            WRITE(21,1350)   efgb(jatom)%qmat(3,1),efgb(jatom)%qmat(3,2), &
>                 efgb(jatom)%qmat(3,3),0.,0.,efgb(jatom)%TENS(3)
>            WRITE(21,1355)   ((efgb(jatom)%eivec(i,j),j=1,3),i=1,3), &
>                 jatom,efgb(jatom)%winkel
>            WRITE(21,1356)  jatom,efgb(jatom)%vzz*24.177d0             
>                               <----
>            WRITE(21,1360)  jatom,efgb(jatom)%eta
>         ENDIF

> 1355 FORMAT(/,9X,'MAIN DIRECTIONS OF THE EFG 
> ',3F8.4,/,36X,3F8.4,/,36X,3F8.4,/,&
>  & ':ANG',i3.3,':',2X,'ANGLE WITH OLD X-AXIS =    ',f8.1)
> 1356 FORMAT(/,':CQ_',i3.3,':',2X, 'QUADRUPOLAR PARAMETER =',F12.5,' 
> MHz IF Q IS EQUAL TO 1b (10-28m^2)')    <----
> 1360 FORMAT(/,':ETA',i3.3,':',25X,'ASYMM. ETA =',F12.5,/,/)

Regards
Florent

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| Florent BOUCHER                    |                                    |
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