[Pw_forum] End of SCF - convergence NOT achieved

Nicola Marzari nicola.marzari at epfl.ch
Wed Jun 28 14:31:45 CEST 2017



In addition to Tom very good suggestions, I'd strongly recommend using
pslibrary 0.3.1 (paw, or ultrasoft), with 90 Ry and dual of 12.

See here for extensive testing of the pseudos:
https://infoscience.epfl.ch/record/216845?ln=en

			nicola


On 28/06/2017 14:14, Tom Daff wrote:
> Hi Ben
>  > It would probably be helpful to see your input file, as there are many
> difficulties with iron and it could be any one of them!
> 
> What magnetism are you using? FCC iron is most stable in antiferromagnetic
> double layer spin state (unless you are willing to look into spin-spiral),
> and around the equilibrium volume there is a crossover in stability of the
> high-spin and low-spin ferromagnetic states and I've found it difficult to
> get convergence if you are off with the starting spin.
> 
> I've found that mixing_beta = 0.1, with the default mixing scheme gives me
> the most efficient convergence, and increasing the number of k-points can
> sometimes help too.
> 
> Tom Daff
> 
> University of Cambridge
> 
> 
> 
> -----Original Message-----
> From: pw_forum-bounces at pwscf.org [mailto:pw_forum-bounces at pwscf.org] On
> Behalf Of Ben Palmer
> Sent: 28 June 2017 08:32
> To: PWSCF Forum <pw_forum at pwscf.org>
> Subject: [Pw_forum] End of SCF - convergence NOT achieved
> 
> Hi Everyone,
> 
> I'm trying to run a scf and vc-relax calculation for FCC Iron (nspin = 2).
> I've managed to do this for a 4 atom example (although the final scf
> calculation did fail: Error in routine ggen (138): smooth g-vectors missing
> !).  When I scale up to 32 atoms, it fails to converge.
> 
> I've increased the number of steps to 250, used Plain, TF and local-TF
> modes, changed the mixing mode, beta and ndim.  I've also tried increasing
> nbnds and changing the starting magnetisation and celldm(1).
> 
> The structure looks fine and I'm using the output from the 4 atom vc-relax
> calculation (scaled up 2x2x2).
> 
> I wanted to ask if anyone has any suggestions on what I could try in order
> to get the calculation to converge?
> 
> Thank you.
> 
> Ben Palmer
> 
> student @ University of Birmingham
> 
> 
> 
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-- 
----------------------------------------------------------------------
Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
Director, National Centre for Competence in Research NCCR MARVEL, EPFL
http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project



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