[Pw_forum] Silent Calculations

Nicola Marzari marzari at MIT.EDU
Sat Aug 9 05:08:55 CEST 2008

Stefano de Gironcoli wrote:
> there should be no incompatibility between shifted grids and phonon 
> calculations.
> stefano

Stefano, all,

let us know if this is still relevant:

the phonons are usually calculated on a regular q-mesh that includes
gamma (I think because of how qtor is written, although nothing would
stop anyone from modifying it to work with a generic q mesh).

Then, if the q-mesh is unshifted, and the k-mesh is shifted, the
cost of the calculation can increase, because all the psi at k+q
are needed, but k+q is not a point in the k-mesh list, unless the
k-mesh (shifted) is fine enough and appropriately chosen so that all
the k+q are in there.


Prof Nicola Marzari   Department of Materials Science and Engineering
13-5066   MIT   77 Massachusetts Avenue   Cambridge MA 02139-4307 USA
tel 617.4522758 fax 2586534 marzari at mit.edu http://quasiamore.mit.edu

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