[QE-users] Relaxation on LaTe3

[Paolo Giannozzi]

There might be a small mismatch, due to numerical reasons, between 
forces and energies, in which case the BFGS minimization will never 
reach the zero-force configuration. You may try to use damped dynamics 
instead. BFGS uses both forces and energies, damped dynamics only forces.

In order to have very precise force values, one needs a highly converged 
scf, but the scf threshold you have used (conv_thr) is very small so I 
don't think this is the origin of the problem

Paolo

On 12/06/2024 16:59, Alejandro Lasso Castillo via users wrote:
> Dear users,
> 
> I am currently trying to perform phonon calculations on LaTe3, and one 
> keypoint in order to have good results is a very well relaxed structure. 
> For this purpose I use a force threshold of 1d-05 (see input file attached).
> 
> However, I find that it is very difficult to achieve this threshold (and 
> it becomes harder when increasing the density of k-points). For a k-grid 
> of 12 x 2 x 12 I try to relax the structure and eventually the bfgs 
> algorithm gets stuck
> into the same three configurations. My strategy so far has been to 
> reintroduce the best structure from the output into the input file and 
> relaunch it but I can not achieve forces less than 6d-05.
> 
> I ask you for some advice in order to achieve my threshold in case you 
> have some experience with this kind of materials.
> 
> *Alejandro Lasso Castillo*
> /Erasmus Mundus Joint Master Student/
> /Quantum Science and Technologies (QUARMEN)/
> 
> 
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 206, 33100 Udine Italy, +39-0432-558216
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