[Pw_forum] phonon calculaiton- shifted k points or not?

[WY]

Dear Paolo, thank you for your answer!

>you mean: "the choice of the q-point grid (i.e. the grid used
>to calculate the interatomic force constants) does not depend
>upon the k-point grid (i.e. the grid used to perform the
>self-consistent calculation")?

Exactly!

>Correct: the former depends
>upon the range of interatomic force constants in real space,
>the latter upon the character of the band structure

Doesn't the above answer agree with what I said in the former post?

>I am not sure that the grid used in the scf calculation
>must be unshifted. What is sure is that the "dense grid"
>must contain all k-points used in the scf calculation and
>all the k+q points, where q are the phonon wavevector
>at which the electron-phonon coefficients are calculated

The problem is: if you choose a shifted k-grid and a unshited q-grid, it 
seems
difficult to maintain the above restrictions-namely the "the "dense grid" 
must
contain all k-points used in the scf calculation and all the k+q points, 
where q
are the phonon wavevector at which the electron-phonon coefficients
are calculated"

Best,

Wen YU