[Pw_forum] IFC's

Eyvaz Isaev eyvaz_isaev at yahoo.com
Sun Sep 2 14:29:04 CEST 2007

Dear Ezad,

--- Ezad Shojaee <ezadshojaee at hotmail.com> wrote:

> i want to know that are we able to use the 'IFC's
> calculated with two grids' together? for example we
> calculate them by a 3*3*3 grid, and then 4*4*4 ,
> then use all of them in calculating C(q) for an
> arbitrary point in the Brillouin zone? 

I do not think so, because of that usually one has to
perform FFT in order to get C(R) of C(q) calculated.
C(q) ==> C(R) is done by q2r.x which needs the same
number of q-points (and dynamical matrices C(q)) which
you used in phonon calculations specifying
nq1,nq2,nq3. Otherwise I assume you will recieve an
error message like "q-point not allowed".

By the way, q2r.x first reads Sysname.dyn0 file which
contains nq1,nq2,nq3 already used and total number of
q-points for this grid, and then q-points. So, if you
like to mix these q-points (and C(q)) which
nq1,nq2,nq3 you can specify in the dyn0 file?



Prof. Eyvaz Isaev, 
Theoretical Physics Department, Moscow State Institute of Steel & Alloys, Russia, and 
Condensed Matter Theory Group, Uppsala University, Sweden Eyvaz.Isaev at fysik.uu.se, eyvaz_isaev at yahoo.com

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