[Pw_forum] q2r.x for a perticular q-point

[Stefano de Gironcoli]

Dear Bipul Rakshit,
 q2r.x is used to generate an interatomic-force constant file (to be 
used with matdyn.x) from a set of matrices corresponding to a 
gamma-centered regular grid of points in the BZ.
  the single K point does not belong to the 1x1x1 grid nor it forms a 
complete 6x6x1 grid... hence the error messages you get.
  ph.x does however compute the frequencies at the end of the run ... so 
what need do you have for q2r.x+matdyn.x ?
  stefano


Bipul Rakshit wrote:
> Dear PWSCF user,
> I am doing phono calculation of graphene sheet.
> If i just want to calculate the frequencies at K point (0.333330  
> 0.577350  0.000000
> ) i am using the following input files
>
>
> *phonons of Graphene
>  &inputph
> ! recover =.true.,
>   tr2_ph=1.0d-14,
>   alpha_mix(1)=0.4,
>   prefix='graphene',
>   amass(1)=12.0107,
>   outdir='./OUT',
>   fildyn='Graph.dyn2',
> !  epsil= .true.,
> !  trans= .true.,
> !  ldisp=.true.
> !  nq1=6, nq2=6, nq3=1
>  lnscf=.true.,
> /
> 0.333330  0.577350  0.000000
> *
>
>
> and q2r.in <http://q2r.in> as
>
> * &input
>     zasr='crystal', flfrc='Graph.fc'
>  /
> 1 1 1
> 1
> Graph.dyn2
> /*
>
> after using q2r.x it gives the error q not allowed, but instead of 1 1 
> 1 if i use 6 6 1, then it gives error 'q point(s) missing'
>
> So is it possible to get the correct phonon frequencies of some 
> individual q-point (in my case K), after using the q2r.x
> and if its possible. Kindly tell me how the inputs should be modified
>
> -- 
> Bipul Rakshit
> Research Fellow,
> S N Bose Centre for Basic Sciences,
> Salt Lake,
> Kolkata 700 098
> India
>
>
> -- 
> Dr. Bipul Rakshit
> Research Associate,
> S N Bose Centre for Basic Sciences,
> Salt Lake,
> Kolkata 700 098
> India
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