[Wien] symmetry broken for Cccm

[Laurence Marks]

Two questions:

a) Is it also wrong with 16.1? That had some accuracy improvements.
b) Is it still wrong when you increase the XC (over)sampling in
case.in0? Fundamentally the x & y axes are different from z in the LM
expansion.

N.B., numerical noise can be larger than one thinks.

On Tue, Jun 27, 2017 at 1:31 PM, mazin <mazin at nrl.navy.mil> wrote:
> Hi,
>
> I am running a pretty standard calculation for the BaFe2As2
> superconductor; have done zillions of those before. For testing
> purposes, I wanted to plot bands for the double-cell AF structure
> (.struct attached), but for the nonmagnetic case and, again, I do think
> I did the same before with no problems. Now I am using the 14.2, and it
> may be that I had used other versions before.
> Without magnetism, this structure is equivalent to I4/mmm (and WIEN2k
> does find this symmetry, if both Fe are made equivalent), so the
> resulting band must, up to numerical noise, possess full tetragonal
> symmetry. Yet, the bands along Gamm-X and Gamm-Y are noticeably
> different (note that in this setting X=(1,0,0), but Y=(0,0,1)).
> If I use the conventional cell (doubled, Pccm), the resulting bands have
> proper symmetry - even though the underlying unit cell is orthorhombic.
> So, the problem appears if the cell is base-centered.
>
> Thanks!



-- 
Professor Laurence Marks
"Research is to see what everybody else has seen, and to think what
nobody else has thought", Albert Szent-Gyorgi
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