[Wien] Force calculations: a problem with Bi

[mazin]

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