[Pw_forum] question about bands calculation

[lan haiping]

Dear Luke,
thanks for you pacient explaination and suggest.

i recalculated this anatase tio2 in succession again with input below, and
found again there were no output about highest occupied and lowest
unoccupied level in the 'bands' output.   i just think it is so strange to
understand, though i could calculate correctly-like bands structure.


kpoints for  'scf'  is using mp grid 8x8x8 without offsets.and kpoint path
for 'bands' calculations is \Gamma[0,0,0] to X [0,0,0.5], from x[0,0,0.5] to
[0.0.5,0.5], from [0.0, 0.5,0.5] to [0.5,0.5,0.5]  ,from[0.5,0.5,0.5] to[0.0
,0.0 ,0.5]
Do you think any fault related to my kpoint path consideration,or any other
parameters in
the input file?



&CONTROL
             title = 'TiO2' ,
       calculation = 'bands',
         verbosity = 'default',
           tprnfor = .true.,
            outdir = '/home/haiping/tmp/',
            prefix = 'tio2',
           disk_io = 'default',
             nstep = 200,
        pseudo_dir = '/home/haiping/espresso-3.0/pseudo/',
        etot_conv_thr= 1.0D-4
        forc_conv_thr= 1.0D-4
/

&SYSTEM
                ibrav= 7,
            celldm(1)=7.1526162323759346,celldm(3)=2.5136063408190221,
               nat = 6 ,
              ntyp = 2 ,
              nbnd = 30 ,
           ecutwfc = 30.0000000000,
           ecutrho = 240.00
       occupations = 'fixed' ,
/

&ELECTRONS
  electron_maxstep = 100,
          conv_thr = 1.0e-12,
       mixing_mode = 'plain' ,
       mixing_beta = 0.300000000,
       mixing_ndim = 8,
   diagonalization = 'cg' ,
/
ATOMIC_SPECIES
O  15.999  O.pbe-rrkjus.UPF
Ti 47.867  Ti.pbe-sp-van_ak.UPF
ATOMIC_POSITIONS angstrom
Ti       0.000000000  -0.946250000  -1.189250000
Ti       0.000000000   0.946250000   1.189250000
O        0.000000000   0.946250000  -0.796426921
O        0.000000000  -0.946250000   0.796426921
O        1.892500000   0.946250000   1.582073079
O       -1.892500000  -0.946250000  -1.582073079
K_POINTS  crystal
 41
0.0 0.0 0.0  1
0.0 0.0 0.1  1
0.0 0.0 0.2  1
0.0 0.0 0.3  1
0.0 0.0 0.4  1
0.0 0.0  0.5  1
0.0 0.05 0.5  1
0.0 0.10 0.5  1
0.0 0.15 0.5  1
0.0 0.20 0.5 1
0.0 0.25 0.5 1
0.0 0.30 0.5 1
0.0 0.35 0.5 1
0.0 0.40 0.5 1
0.0 0.45 0.5 1
0.0 0.50 0.5 1
0.05 0.50 0.5 1
0.10 0.50 0.5 1
0.15 0.50 0.5 1
0.20 0.50 0.50 1
0.25 0.50 0.50 1
0.30 0.50 0.50 1
0.35 0.50 0.50 1
0.40 0.50 0.50 1
0.45 0.50 0.50 1
0.50 0.50 0.50 1
0.467 0.467 0.50 1
0.433 0.433 0.50 1
0.400 0.400 0.50 1
0.367 0.367 0.50 1
0.333 0.333 0.50 1
0.30  0.30  0.50 1
0.267 0.267 0.50 1
0.233 0.233 0.50 1
0.20  0.20 0.50  1
0.167 0.167 0.50 1
0.133 0.133 0.50 1
0.100 0.100 0.50 1
0.067 0.067 0.50 1
0.033 0.033 0.50 1
0.00  0.00  0.50 1



Yours,

hai-ping




On 10/23/06, lukethulin at netscape.net <lukethulin at netscape.net> wrote:
>
>  hai-ping,
>
> I've successfully done band structure modeling for anatase, I'll go back
> and find what I chose for high symmetry lines, or find the reference I
> used.  I guess I just thought it was strange that the nscf calculations were
> being done separately, when you could just pick several paths and do them
> all in one calculation.
>
> Luke
>
> ----- Original Message -----
> *From:* lan haiping <lanhaiping at gmail.com>
>  *To:* pw_forum at pwscf.org
> *Sent:* Monday, October 23, 2006 12:38 AM
> *Subject:* Re: [Pw_forum] question about bands calculation
>
>
> Dear Luke,
> thanks for your reply. my structure is anatase titania.
> Actually, i set the k-point paths according to high symmetry lines such as
> \Gamma[0,0,0] to Z [0,0,0.5] , Z to Q[0,0.5,0.5]  etc.
> Is it right ?
>
> Regards,
> hai-ping
>
>
> On 10/22/06, lukethulin at netscape.net <lukethulin at netscape.net> wrote:
> >
> >  Hai-ping,
> >
> > I don't think you're going about a band structure calculation
> > correctly.  The scf calculation should only use automatic k-point selection
> > of (4,4,4) or something like that.  The following nscf calculation needs you
> > to input k-paths along high symmetry lines that vary by crystal structure.
> > What form of titania are you modeling, anatase, rutile?
> >
> > Luke
> >
> > ----- Original Message -----
> > *From:* lan haiping <lanhaiping at gmail.com>
> > *To:* pw_forum <pw_forum at pwscf.org>
> > *Sent:* Saturday, October 21, 2006 2:31 PM
> > *Subject:* [Pw_forum] question about bands calculation
> >
> >
> > Hi!
> >
> >   i have a question about bands calculation .
> >  Just after finished a '*scf*' calculation for tio2, i performed a
> > series (about 5)  '*nscf*' calculations with  different k-grid paths.
> > Except k-grid path, all settings are the same for these series ' nscf '
> > calculation.
> > In some nscf-output,  the values of "Highest occupied level and lowest
> > unoccuped level"  are  found. But  these values are not found in the other
> > nscf-output . I donot know what the reasons are related to . Morever, i also
> > came to a calculation failed with complains "Too many eigenvalues are not
> > converged".
> >
> > Regards,
> > hai-ping
> >
> >
> >
> >
>
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