[Pw_forum] help for convergence in "Computing Second order response"

Paolo Giannozzi giannozz at nest.sns.it
Tue Oct 30 21:54:28 CET 2007

On Oct 26, 2007, at 7:14 , hyello25 Qgrui wrote:

>  When I do raman calculation of Li2O, I found the "second order  
> response"
> process is not convergent.

try to reduce the alpha_mix parameter

>  What is more wried, this situation never happened days before when
> using the exactly same input file and PPs. That is , I cannot  
> repeat the
> result again with all the same input file though I check all the  
> input file
> carefully. The scf result are the same, but the ph.x gave different
> convergence process. Besides, I got different raman frequencies.

you are not doing the same calculation. Computers are deterministic,
even if it often happens that they look like random number generators

Paolo Giannozzi, Dept of Physics, University of Udine
via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222

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