[Pw_forum] Low q phonon mode.

[Eyvaz Isaev]

Hi,

From: Bipul Rakshit <bipulrr at gmail.com>
> The kinetic energy and charge density are 40 and 480 Ry
> using 36x36x1 and 100, 2800 Ry.

Please keep in mind the cutoff energy is a characteristic feature of a 
pseudopotential, especially for US and PAW. "ecutrho" can be obtained doing some 
test calculations. Anyway, you should do some tests, if you are not sure which 
ecutwfc and ecutrho are to be applied. 


> so i just want to ask, whether is it meaningful to do calculation with higher 
>precision to obtain the dynamical matrices *.dyn1 and *.dyn2 using 36x36x1 and 
>100, 2800 Ry.

I think you will kill your supercomputer with these parameters. May be it is 
worth doing several phonon tests  for a particular small q-point  varying  
ecutwfc, ecutrho and k-mesh. Then decide, which parameters are better for you. 


Bests,
Eyvaz.
-------------------------------------------------------------------
Prof. Eyvaz Isaev, 
Department of Physics, Chemistry, and Biology (IFM), Linkoping University, 
Sweden 

Theoretical Physics Department, Moscow State Institute of Steel & Alloys, 
Russia, 

isaev at ifm.liu.se, eyvaz_isaev at yahoo.com