[Pw_forum] missing q-points

[Eyvaz Isaev]

Hi,

If you use kpoints.x to generate 2x2x1 k-mesh for graphene you will find 2 q-points with weights 1 and 3, respectively (total 4 points, reduced to 2 by symmetry). But according to your message q2r.x reports only 2 points totally (1+1) that is incorrect (2x2x1 = 4) . Different number of q-points usually tells us something is wrong. As example, for WC-type structure with c/a \approx 1 the use of 4x4x2 grid leads to the same error, but 4x4x4 is OK. At the same time, usually  4x4x2 is OK for hexagonal structures.  

Hopefully, now you understand why I asked you to generate q-points.

So, you could first generate q-points using kpoints.x, calculate the dynamical matrices for these q-points and then apply q2r.x. 

Or follow Gabriele's advice.

Bests,
Eyvaz.

-------------------------------------------------------------------
Prof. Eyvaz Isaev, 
Theoretical Physics Department, Moscow State Institute of Steel & Alloys, Russia, 
Department of Physics, Chemistry, and Biology (IFM), Linkoping University, Sweden 
Condensed Matter Theory Group, Uppsala University, Sweden 
Eyvaz.Isaev at fysik.uu.se, isaev at ifm.liu.se, eyvaz_isaev at yahoo.com


--- On Wed, 6/10/09, Gabriele Sclauzero <sclauzer at sissa.it> wrote:

> From: Gabriele Sclauzero <sclauzer at sissa.it>
> Subject: Re: [Pw_forum] missing q-points
> To: "PWSCF Forum" <pw_forum at pwscf.org>
> Date: Wednesday, June 10, 2009, 5:31 PM
> I tried to reproduce your error but I
> couldn't. I've used the cvs version of QE on my 
> Linux Intel PC and I could obtain the interatomic force
> constants without any error 
> message. Here is the output from q2r
> 
> [sclauzer at brenta:~/tmp/Graphene]$
> /scratch/sclauzer-exec/espresso-4.1CVS/bin/q2r.x < 
> anvari.q2r.in | tee anvari.q2r.out
>    reading grid info from file
> graphene.dyn0
>    reading force constants from file
> graphene.dyn1
>    Dielectric Tensor not found
>    nqs=         
>   1
>   q=   0.00000000 
> 0.00000000  0.00000000
>    reading force constants from file
> graphene.dyn2
>    nqs=         
>   3
>   q=   0.00000000 -0.60905451 
> 0.00000000
>   q=   0.52745668 
> 0.30452725  0.00000000
>   q=  -0.52745668  0.30452725 
> 0.00000000
> 
>        q-space grid ok, #points
> =    4
> 
>        fft-check warning: sum of
> imaginary terms = .8800000E-06
> 
> If you used an older version of QE, please try with the
> latest 4.0.5 or the CVS one.
> 
> Regards,
> 
> Gabriele
> 
> Mehrnaz Anvari wrote:
> > 
> > Hi
> > First I have to say as Eyvaz had suggested I ran my
> ph.x code for same 
> > nq1,nq2,nq3 (2,2,2) but I get the previous error. I
> ran kpoints.x but I 
> > did'nt understand how could it help me, because I have
> done scf 
> > calculations with 12x12x1 grid and I have got same k
> as I got from 
> > kpoints.x.
> > In the following as you wanted you could check some
> parts of my input & 
> > output.
> > _*scf calculations*_
> > /
> > &system
> > ibrav = 0 , celldm(1) =4.92 , nat= 2, ntyp= 1,
> > ecutwfc =35, ecutrho=500 , occupations='smearing',
> degauss=0.02,
> > smearing='m-p',
> > /
> > &electrons
> > diagonalization='cg'
> > mixing_beta = 0.7
> > conv_thr = 1.0d-9
> > /
> > ATOMIC_SPECIES
> > C 12.0107 C.pbe-van_bm.UPF
> > CELL_PARAMETERS HEXAGONAL
> > 0.947945153 0.000000000 0.000000000
> > -0.473972577 0.820944584 0.000000000
> > 0.000000000 0.000000000 10.017908940
> > ATOMIC_POSITIONS {crystal}
> > C 0.000000000 0.000000000 0.000000000
> > C 0.333333300 0.666666700 0.000000000
> > K_POINTS AUTOMATIC
> > 12 12 1 1 1 1
> > 
> > _*phonon calculations*_
> > 
> > tr2_ph=1.0d-14,
> > prefix='Graphene',
> > ldisp=.true.,
> > nq1=2, nq2=2, nq3=1
> > amass(1)=12.0107,
> > outdir='/home/mehrnaz/scratch/tmp2/',
> > fildyn='graphene.dyn',
> > /
> > 
> > _*q2r.out*_
> > nqs= 1
> > q= 0.00000000 0.00000000 0.00000000
> > reading force constants from file graphene.dyn2
> > nqs= 1
> > q= 0.00000000 -0.60905451 0.00000000
> > 
> > from init : error # 1
> > missing q-point(s)!
> > stopping ...
> > Mehrnaz
> > Iran University Of Science & Technology
> > 
> >  
> > 
> > 
> >
> ------------------------------------------------------------------------
> > 
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> 
> -- 
> 
> 
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> | Gabriele Sclauzero, PhD Student     
>             |
> | c/o:   SISSA & CNR-INFM
> Democritos,             
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