[Wien] Force calculations: a problem with Bi

[Peter Blaha]

Checking your case.struct I can see that all R0 values are equal and
rather big (R0=0.0001).

Try to generate the struct-file with w2web, it will create a much 
smaller R0 (an order of magnitude ?)

mazin schrieb:
> Laurence Marks wrote:
> 
>  > Which version of Wien2k? Centro-symmetric or not? How big is the
>  > discontinuity at the RMT, and how large are the distances between the
>  > atoms (if too small there can be problems)? What are the RMT's (maybe
>  > attach the struct file, as well as in1/in2.
> 
> (1) The result does not change between the WIEN2k_07 and WIEN2k_09.
> (2) The group is P4/nmm, obviously centrosymmetric, although I do not 
> see why that should matter as long as I am doing nonmagnetic stuff
> (3) That is the first thing that comes to mind. Bi is somewhat 
> unnaturally squeezed in this compound. I do not know of any easy way to 
> read off discontinuity just from the output files, but I did vary the MT 
> radii quite a bit (within 20%), and the results barely changed. I also 
> verified that increasing LMMAX in .in2 does not affect anything.
> (4) The struct file follows, but before I briefly reply to Stefaan:
> 
> Stefaan Cottenier wrote:
> 
>  > * Do you have FOR (instead of TOT) in case.in2(c) in the last
>  > iteration? Otherwise Pulay corrections are not taken into account, and
>  > that might explain your observations.
>  > Do you use spin-orbit coupling? Forces in wien2k are not consistent
>  > with spin-orbit.
> 
> As I mentioned, I calculate forces, so of course I'd Pulay turned on. 
> AAMOF, speedup by turning them off is really minor, I do not see why it 
> actually defaults to TOT. Tradition I guess.
> 
> I also said explicitly that the calculations were scalar-relativistic.
> 
> By my rough estimate, this is about the hundredth system (not the 
> compound, the system!) I have been doing with WIEN, and I do not recall 
> any case of such a bizarre discrepancy, except one occasion when I just 
> ignored it, and my recollection is it was also with Bi. I will try to 
> dig out that calculation, too. Something very specific is going on here. 
> I am seriously puzzled.
> 
> OK, here is the relevant part of the struct file:
> 
> P   LATTICE,NONEQUIV.ATOMS:  4129_P4/nmm
> MODE OF CALC=RELA
>   7.37353   7.37353  16.34802  90.000000 90.000000 90.000000
> ATOM  -1: X=0.25000000 Y=0.25000000 Z=0.13600000
>           MULT= 2          ISPLIT=-2
>       -1: X=0.75000000 Y=0.75000000 Z=0.86400000
> Bi         NPT=  781  R0=0.00010000 RMT=   2.31      Z: 83.0
> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>                      0.0000000 1.0000000 0.0000000
>                      0.0000000 0.0000000 1.0000000
> ATOM  -2: X=0.75000000 Y=0.25000000 Z=0.50000000
>           MULT= 2          ISPLIT=-2
>       -2: X=0.25000000 Y=0.75000000 Z=0.50000000
> Cu         NPT=  781  R0=0.00010000 RMT=   2.37      Z: 29.0
> LOCAL ROT MATRIX:    0.7071068-0.7071068 0.0000000
>                      0.7071068 0.7071068 0.0000000
>                      0.0000000 0.0000000 1.0000000
> ATOM  -3: X=0.25000000 Y=0.25000000 Z=0.66700000
>           MULT= 2          ISPLIT=-2
>       -3: X=0.75000000 Y=0.75000000 Z=0.33300000
> S          NPT=  781  R0=0.00010000 RMT=   2.10      Z: 16.0
> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>                      0.0000000 1.0000000 0.0000000
>                      0.0000000 0.0000000 1.0000000
> ATOM  -4: X=0.75000000 Y=0.25000000 Z=0.00000000
>           MULT= 2          ISPLIT=-2
>       -4: X=0.25000000 Y=0.75000000 Z=0.00000000
> O          NPT=  781  R0=0.00010000 RMT=   1.95      Z:  8.0
> LOCAL ROT MATRIX:    0.7071068-0.7071068 0.0000000
>                      0.7071068 0.7071068 0.0000000
>                      0.0000000 0.0000000 1.0000000
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