[Wien] Re: [WIEN]: Antiferromagnetic Computations

[cbridges]

Dear All,
 I would like to perform an AFM calculation for bcc Cr, as below, but
using the runafm_lapw script. I have found that procedure (1) below
(using runsp_lapw) works. However, I can't get the other procedure to
work. This should involve:

x afminput
view outputafminput
view inclmcopy_st
copy inclmcopy_st
runafm_lapw

Could someone who has successfully used runafm_lapw for bcc Cr
possibly suggest what is wrong? In fact, it is possible to get to the
runafm_lapw stage successfully, but the run stops after one cycle with
an error in mixer.

I note that the manual (section 4.5.4 UG) states that case.inst must
be modified in the same way as for the runsp_lapw calculation, so I
don't understand why runsp_lapw would work, when runafm_lapw will not.
The UG says that runafm_lapw will not work in all cases, but I
expected that it might for bcc Cr as it is the example.

One final note is that after choosing 'yes' for 'Perform
Antiferromagnetic Calc?', we are asked if case.inst has been edited.
After choosing 'edit case.inst' and going through all of the required
steps, we are later again faced with the same question. However,
choosing 'Yes, continue' does not seem to do anything, as 'x afminput'
is not highlighted. This is probably not serious, but it is perhaps
worth mentioning.

Regards,
Craig





--------------- reply ----------------
> ====
> Stefaan Cottenier <Stefaan.Cottenier at fys.kuleuven.ac.be>
> submitted the following contribution:
> ====
> 
> 
> > ====
> > "Trevor A. Tyson" <tyson at adm.njit.edu>
> > submitted the following contribution:
> > ====
> > 
> >     Can someone tell me what the procedure is for setting-up
> > an antiferromagetic computation for bcc Cr (a=2.88 A)?  Can you
send
> >   sample input files?
> 
> You have two choices:
> 
> 1) Take two Cr atoms at inequivalent positions (i.e. CsCl
structure:)
> 
> Title
> P                            2
> MODE OF CALC=RELA
>   5.102263  5.102263  5.102263 90.000000 90.000000 90.000000
> ATOM   1: X=0.00000000 Y=0.00000000 Z=0.00000000
>           MULT= 1          ISPLIT= 2
> Cr1        NPT=  781  R0=.000500000 RMT= 2.20000     Z:24.0
> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>                      0.0000000 1.0000000 0.0000000
>                      0.0000000 0.0000000 1.0000000
> ATOM   2: X=0.50000000 Y=0.50000000 Z=0.50000000
>           MULT= 1          ISPLIT= 2
> Cr2        NPT=  781  R0=.000500000 RMT= 2.20000     Z:24.0
> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>                      0.0000000 1.0000000 0.0000000
>                      0.0000000 0.0000000 1.0000000
> 
> And then manually edit the case.inst in order to make the two Cr
antiferromagnetic:
> 
> Cr
> Ar 3 5
> 3, 2,2.0  N
> 3, 2,2.0  N
> 3,-3,1.0  N
> 3,-3,0.0  N
> 4,-1,1.0  N
> 4,-1,0.0  N
> Cr
> Ar 3 5
> 3, 2,2.0  N
> 3, 2,2.0  N
> 3,-3,0.0  N
> 3,-3,1.0  N
> 4,-1,0.0  N
> 4,-1,1.0  N
> ****
> ****         END of input (instgen_lapw)
> 
> Now initialize as for a regular spinpolarized calculation.
> 
> 2) Use the default case.inst, and then choose the antiferromagnetic
option at
> the end of init_lapw. This saves half of the calculation time, but
I'm not
> familiar with the input for this AF option.
> 
> Stefaan
> 
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