[Pw_forum] End of SCF - convergence NOT achieved

[Nicola Marzari]

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