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["Josef W. Zwanziger" <jzwanzig@jzwanzig.org>]

Hi, I can't repeat what you are finding. If I explicitly break the BCC symmetry of iron by straining the sample, it doesn't change the convergence with respect to the value of ecutsm at all. I have also used ecutsm to optimize cell geometries in lots of non-cubic cases, and never had a problem like what you are describing. I'm stuck. Maybe someone else can be more helpful?

Joe

 

Josef W. Zwanziger
Professor of Chemistry
Canada Research Chair in NMR Studies of Materials
Director, Atlantic Region Magnetic Resonance Centre
Department of Chemistry
Dalhousie University
6274 Coburg Road
Halifax, Nova Scotia B3H 4J3 Canada
tel: +1.902.494.1960
fax: +1.902.494.1310
web: http://jwz.chem.dal.ca
jzwanzig@jzwanzig.org,jzwanzig@dal.ca

---

From: Emmanuel Arras <emmanuel.arras@cea.fr>
To: forum@abinit.org
Sent: Friday, December 12, 2008 2:40:23 PM
Subject: Re: [abinit-forum] ecutsm and electronic convergence

Ok, I think found the problem. In fact, it happens when the box is non-isotropic :
Here are the plots of the electronic convergences ( deltaE(h) ) vs SCF steps for 4 calculations :
Fe-BCC_ecutsm_iso :  smearing = 0 and 1, on a cubic box (acell 3*2.9 angstrom)
Fe-BCC_ecutsm_aniso : smearing = 0 and 1, on a non-cubi box (acell 2*2.9 3.1 angstrom)
the output given is the one for non-cubic box and smearing = 1.
What do you think?


Emmanuel Arras a écrit :

I will try this on Fe BCC. Maybe it is linked with my pseudo, or my system (which is quite specific).
Thanks for your response. I'll keep you posted.

Emmanuel ARRAS

Josef W. Zwanziger a écrit :

This is odd. I've done lots and lots of PAW calc's, with ecutsm and without, on magnetic and non-magnetic systems, and have never observed anything like what you're describing. Can you post your input file?

 Josef W. Zwanziger
Professor of Chemistry
Canada Research Chair in NMR Studies of Materials
Director, Atlantic Region Magnetic Resonance Centre
Department of Chemistry
Dalhousie University
6274 Coburg Road
Halifax, Nova Scotia B3H 4J3 Canada
tel: +1.902.494.1960
fax: +1.902.494.1310
web: http://jwz.chem.dal.ca
jzwanzig@jzwanzig.org,jzwanzig@dal.ca



----- Original Message ----
  

From: Emmanuel Arras <emmanuel.arras@cea.fr>
To: forum@abinit.org
Sent: Thursday, December 11, 2008 1:27:40 PM
Subject: [abinit-forum] ecutsm and electronic convergence

Dear abinit users,
   I have observed that the use of ecutsm (typically 0.5 Ha for a cutoff 
of 10 Ha, ecut CV around e-2 eV/atom) makes it very difficult for abinit 
to achieve convergence : i.e. over 200 iterations to reach e-8 in toldfe 
(despite a steady slope), as compared to the 30 usually needed 
iterations. I am wondering where this comes from, and how to solve this 
issue.
  Note that I am using paw, and that my system is magnetic. It seems in 
fact that magnetism is hugely affected by this ecutsm : it takes much 
more time to reach final value (whereas magnetism is usualy very quick 
to converge). Also note that whatever the cutoff (up to 20 Ha, which is 
huge in paw), this problem appears.

Thanks for any advices.

Emmanuel ARRAS