[Wien] Force calculations: a problem with Bi

[Rocquefelte]

I also looked at systems containing bithmuth atoms some times ago and I 
just remember that Bi should be treated with care:
- problem of the description of the 6s lone pair electron
- necessity or not to add spin-orbit to properly describe the effect of 
this heavy element on the band structure.

In your case, would it be possible that the problem you have to solve is 
related to the difficulty to properly describe the 6s(Bi) lone pair 
electrons?

Regards

Xavier


mazin a écrit :
> 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
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>