[Pw_forum] occupations fixed

[Lorenzo Paulatto]

In data 07 ottobre 2009 alle ore 10:32:28, udayagiri sai babu  
<udayagiri3 at gmail.com> ha scritto:

> Dear Lorenzo thanks for the answer. My problem is simple it is to find  
> out the cohesive energy of Cr,V,Ti. I posted this question earlier also.  
> I was told to try out with occupations=from_input instead of degauss  
> value to get the accurate value of the ground state energy because i am  
> getting an error of around 10% in Ec (i was wondering if that can be  
> acceptable) meanwhile i came across the post which says to use  
> ocuupations=fixed.

Isolated Cr, V and Ti all have magnetic ground state, you have to take  
care in making the calculation for the isolated atom with spin and with  
some initial magnetization. It would be even better to compute it with and  
without spin, so you can see the difference.

V and Ti have a ground state which is NOT spherical, you absolutely must  
use *nosym=.true.*, and break the symmetry somehow, e.g. by specifying  
occupations from input, or tot_magnetization or multiplicity; or taking a  
slightly non-cubic unit cell.

Best regards.


-- 
Lorenzo Paulatto
SISSA  &  DEMOCRITOS (Trieste)
phone: +39 040 3787 511
skype: paulatz
www:   http://people.sissa.it/~paulatto/

     *** save italian brains ***
  http://saveitalianbrains.wordpress.com/