[Pw_forum] Vc-relax again

[Elio Physics]

Hello all,
I am still having a problem with relaxing a structure (hexagonal).. The initial pressure was calculated to be -12 kbars. I managed to reduce the pressure to 0.02 and the total force to 0.0007 using vc-relax. However when I ran a scf calculation on the relaxed structure , the pressure was again -16 and the total force 0.4.  Professor Paolo G. gave me a link for this problem.. I understood that I need  to  increase the  cutoff kinteic energy which I did and I realized that the pressure goes down but to -6; however the total force is still 0.4! 
(1) Anyone knows how to solve this problem.
I have run the calculation again wih ibrav=0 instead of ibrav=6 and the crystal axes were:
              a(1) =   (   0.492694   0.853319   0.000001 )               a(2) = (   0.492685  -0.853314  -0.000001 )               a(3) = (   0.000001   0.000004   4.274389 )
The pressure was -0.02 and the total force was 0.001 which was fine in both scf and vc-relax. However when I redid an scf calculation with ibrav=6 with c/a =4.274389 (which I read from the ibrav=0 calculation with the same atomic positions of the "ibrav=0" calculation), I still got P =-16 and total force=0.4.  I was trying to convert the ibrav=0 input to ibrav=6..did I do anything wrong?

Any help would be appreciated 
Thanks
Elio Nahdan
 		 	   		  
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