[Pw_forum] Bands.x not ordering bands correctly

[Henry J Seeley]

"Make pp" should have worked, it generated a new bands.x executable at 
least.
I did not have lsym = true, though. What exactly does this do? I read 
the info on the bands.x input description page, but it was not very 
clear.

I am now using lsym = true, and I am getting the following message:
"
      Message from routine punch_plottable_bands:
      two consecutive same k, exiting
"

Will this produce any error in my results?

Thank you,
Hank Seeley



On 2016/01/15 00:04, stefano de gironcoli wrote:
> did "make pp" recompile the bands.x code ?
> is the input flag lsym=.true. ?
> stefano
> 
> On 15/01/2016 02:47, Henry J Seeley wrote:
>> Stefano (or anyone else who may know a solution to this issue),
>> 
>> I uncommented the write line, and used "make pp" to remake my bands.x
>> executable, but I am not obtaining any print-outs of abs(pro). How can 
>> I
>> get this information to appear?
>> 
>> -Hank
>> 
>> 
>> On 2016/01/13 14:29, stefano de gironcoli wrote:
>>> Hi Hank,
>>>     bulk PbS has 2 atom per cell. why do you need 20-30 ?
>>> 
>>>     bands.x "follows" a band based on the overlap of the wfcs in two
>>> neighboring points..
>>>     it accepts the band on the basis of a rather small overlap 
>>> threshold
>>> 
>>> ... somewhere around line 350 in $espresso_root/PP/src/bands.f90
>>> pro=cgracsc(nkb,becp%k(:,jbnd),becpold%k(:,idx(ibnd)), &
>>>                            nhm, ntyp, nh, qq, nat, ityp, ngm, NEW, 
>>> old,
>>> upf)
>>>                    ENDIF
>>> !                 write(6,'(3i5,f15.10)') ik,idx(ibnd), jbnd, 
>>> abs(pro)
>>>                    IF (abs (pro) > 1.d-2 ) THEN
>>>                       il (idx(ibnd),ik) = jbnd
>>>                       GOTO 10
>>>                    ENDIF
>>> ...
>>> 
>>>      this is probably ok in most cases when there are few bands to 
>>> chose
>>> from and only one is the "right one". In your case there are many 
>>> bands
>>> and maybe there are many not too wrong bands that fulfill the
>>> threshold..:-(
>>>      I would try to
>>>      1) uncomment the write statement and see what are the typical
>>> values
>>> of abs(pro) you get.
>>>        if everything is fine there should be only one jbnd band for 
>>> each
>>> idx(ibnd) band that is significantly different from zero (much more
>>> than
>>> 1.d-2 i would expect).. If you have more than one jbnd band that
>>> exceeds
>>> the threshold for a given examined idx(ibnd) then the code may do the
>>> wrong assignment
>>>      2) if this is the origin of the problem i would try to play with
>>> the
>>> threshold to induce the code to make the proper assignment
>>> 
>>>      using a finer k point grid should also work but I would say that 
>>> 15
>>> points in a 20-30 atom cell should already be enough !
>>> 
>>>     good luck,
>>> 
>>>     stefano
>>> 
>>> On 13/01/2016 21:52, Henry J Seeley wrote:
>>>> Hello everyone,
>>>> 
>>>> I'm using bands.x to assign eigenvalues to specific bands of PbS. I
>>>> have
>>>> fairly large supercells (20-30 atoms), so my bands are dense with 
>>>> lots
>>>> of crossings. When I run bands.x it incorrectly assigns bands
>>>> resulting
>>>> in erratic band diagrams (e.g., bands suddenly jump across the 
>>>> bandgap
>>>> to connect conduction and valence eigenvalues). What are the 
>>>> potential
>>>> causes of this error?
>>>> 
>>>> Perhaps I am not sampling my k-points densely enough; I have
>>>> approximately 10-15 points per sampling line. I plan on increasing
>>>> this
>>>> density to 50 kpts per line, and will report back if this solves the
>>>> problem. I am somewhat in a rush to get these results though, so if
>>>> anyone has some insight it would be much appreciated.
>>>> 
>>>> Also, assuming there is a solution to this problem, is band.x 
>>>> capable
>>>> of
>>>> sorting a 2D grid of kpoints into bands? I am interesting in
>>>> generating
>>>> contour maps.
>>>> 
>>>> Thank you,
>>>> Hank Seeley
>>>> Chemistry PhD student
>>>> University of Oregon
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