[Pw_forum] ambiguity in stress calculation
Javad hashemifar
jhashemifar at gmail.com
Mon Dec 18 12:23:28 CET 2006
Dear Pwscf users
Concerning the "tstress" input variable in the namelist 'control', I
found the following explanation in the prepared sample INPUT_PW file:
tstress LOGICAL
calculate stress. Set to .TRUE. if calculation='vc-md'
Does it mean that the calculated stress for other type of calculations
(such as 'scf' and 'relax') is meaningless and is incorrect. I mean if
we set tstress=.TRUE. in calculations='relax' then obtained stress
values are correct or not.
Thanks in advance for your answers
Javad Hashemifar
On 12/17/06, Malgorzata Wierzbowska <wierzbom at ts.infn.it> wrote:
> On Sun, 17 Dec 2006, Amit Kumar wrote:
>
>
> In the k-points input we read a line with numbers
> nk1 nk2 nk3 k1 k2 k3
> where (k1,k2,k3) is a shift-vector from the origin.
> For the el-ph calculation (and I guess also for the integration
> with the tetrahedra method) we need to specify k1=k2=k3=0
>
> ---- So your "32 32 4 1 1 1" for sure is wrong.
> You need to take "32 32 4 0 0 0".
>
> You are right that all k and k+q have to belong to the dense grid.
> But see: All your meshes are in the same BZ and they are generated
> by division of the reciprocal lattice vectors b1,b2,b3 by numbers
> nk1, nk2, nk3 (above is true also for q-point grid nq1, nq2, nq3).
>
> To check whether your your k and k+q are in dense k-mesh,
> You need to see whether dense nk1 divided by rare nk1 gives integer
> and whether dense nk1 divided by nq1 gives integer.
> If above 2 conditions are satisfied, you check direction b2 and b3
> in your cell: I mean dense_nk2/nq2 and dense_nk3/nq3
> and dense_nk2/rare_nk2 etc. If all above give integers --
> which is your case -- your error does not occur.
>
> -- So let us check your meshes:
> dense 32 32 4 0 0 0
> rare 8 8 1 0 0 0
> phonon 4 4 1 (it should be default here that they are not shifted)
>
> direction b1: 32/8=integer, 32/4=integer, also k+q is OK because 8/4=integer
> the same for b2
> direction b3: 4/1=integer
>
> For me it works for hehagonal Mg. Please do my excercise I attach the script.
>
> Gosia
>
>
>
>
> > Dear Malgorzata,
> >
> > It's very nice to recieve your useful suggestions.
> > I tried all the combinations--->
> > 32 32 4 0 0 0, 32 32 32,
> > 32 32 4 1 1 1 --->>> every possible combinations before posting this
> > problem on the forum.
> > But I got the same following error again and again.
> >
> > electron-phonon interaction ...
> >
> >
> > %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> > from lint : error # 23
> > cannot remap grid on k-point list
> > %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> >
> > stopping ...
> >
> >
> > I think the source of the above error is something different.
> >
> > My guess::::
> >
> > The dense grid must contain all k and k+q grid points used in the
> > e-p calculation.
> >
> > How do we know the above condition has been satisfied for automatic
> > generated k and q points with nk1=32, nk2=32, nk3=4 and
> > nq1=4, nq2=4, nq3=1??????
> >
> > Here is my q-point grid::::
> >
> > Calculation of the dynamical matrices for ( 4, 4, 1,) uniform grid of
> > q-points
> > ( 7q-points):
> > N xq(1) xq(2) xq(3)
> > 1 0.00000 0.00000 0.00000
> > 2 0.00000 0.28868 0.00000
> > 3 0.00000 -0.57735 0.00000
> > 4 0.25000 0.14434 0.00000
> > 5 0.25000 0.43301 0.00000
> > 6 -0.50000 -0.28868 0.00000
> > 7 -0.50000 0.00000 0.00000
> >
> > And my k-points grid is here::::
> >
> > number of k points= 166 gaussian broad. (ryd)= 0.0100 nga
> > uss = 1
> > cart. coord. in units 2pi/a_0
> > k( 1) = ( 0.0000000 0.0000000 0.0000000), wk = 0.0
> > 312500
> > k( 2) = ( 0.0000000 0.2886751 0.0000000), wk = 0.0
> > 000000
> > k( 3) = ( 0.0000000 0.1443376 0.0000000), wk = 0.0
> > 104167
> > k( 4) = ( 0.0000000 0.4330127 0.0000000), wk = 0.0
> > 000000
> >
> > *
> > *
> > * k( 166) = ( 0.2500000 0.8660254 0.0000000), wk = 0.0000000
> >
> > See!!!! 0.28868 and 0.2886751 are not exactly equal.
> >
> > Is this the possible reason for the error like
> > "cannot remap grid on k-point list"?????
> >
> > I'm not sure any other there might be any other.
> > Please help me to find out the unknown reason of this well known
> > error and give me some clue to get rid of this error.
> >
> > Thank you again for your very very useful letter.
> >
> > Regards,
> > Amit
> >
> >
> >
> >>
> >
>
>
--
======================================
Seyed Javad Hashemifar, Ph.D.
[current:]
Tel:+49-203-3794743 Fax:+49-203-3794742
Fachbereich Physik (AG Kratzer), Universitat Duisburg-Essen
47048 Dusiburg, Germany
[permanent:]
Tel: +98-311-3912375 Fax: +98-311-3912376
Physics Department, Isfahan University of Technology
84156 Isfahan, Iran
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