[Pw_forum] K-point in phonon calculation

[Lo_wan_2005XW]

Dear developer and users:

Exactly follow the userguide, I am trying to calculate the phonon.

Firstly I make a self-consistent calculation with 
K_POINTS automatic
8 8 8   0  0  0

After the calculation convergent, I start the ph.x calculation. But the calculation is extremely slow, thus I goto
the output-file, and find a strange thing.

For some q-qoint, I find;
number of k points=  1024  Marzari-Vanderbilt smearing, width (Ry)=  0.0500

I understand that phonon may break some symmetry, but how it can go to 1024-k-point when I use 8-8-8 mesh?

I already use "start_q=X, last_q=X, recover=.true.," to separate q-point. I also use parallel to speed up the calculation.
But it is still extremely slow. My system has only 12 atoms per unit cell, and it seems that some q-point 
(where it requires 1024 k-points) may need one month!

I don't know if there is other method to speed up the calculation?

Thanks!

Xiangang Wan



 		 	   		  
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