[Pw_forum] Problems Computing Cholesky for VC-Relax of MnO2

[Lance Kavalsky]

Dear All,


Thank you all for your suggestions.


I am no longer getting the error after increasing the energy cutoff of the wavefunctions to 250.0 Ry, decreasing the smearing to 0.01, and resetting the diagonalization back to davidson.


I have experimented with varying the starting magnetizations and it consistently converges to a non-magnetic state. However, M. Kan et al. showed that a ferromagnetic state should exist via DFT (J. Phys. Chem. Lett., 2013, 4 (20), pp 3382–3386). Is this lack of magnetic states in my investigations more likely a result of not yet discovering a suitable starting magnetization, or could there be another reason such as choice of pseudopotentials?


Thanks again,


Lance Kavalsky

MASc student


Dept. of Materials Science and Engineering

University of Toronto




________________________________
From: pw_forum-bounces at pwscf.org <pw_forum-bounces at pwscf.org> on behalf of Lorenzo Paulatto <lorenzo.paulatto at impmc.upmc.fr>
Sent: Saturday, September 2, 2017 3:48:11 AM
To: pw_forum at pwscf.org
Subject: Re: [Pw_forum] Problems Computing Cholesky for VC-Relax of MnO2

On 01/09/17 23:04, Lance Kavalsky wrote:
    nspin=2,
    lda_plus_u=.TRUE.
    hubbard_U(1)= 3.9
    starting_magnetization(1)=0.5
   starting_magnetization(2)=-0.5

I would be that it is the GGA+U correction that is causing problems, not the position of the atoms. Does your calculation converge without the +U? Does it converge wit ha very small +U value?

I also think, your smearing is a bit large for the number of k-points you have, this should not be a problem for convergence, but can affect the accuracy of your results.

    diagonalization = 'cg'

Don't use CG, it is slow and does not converge "better" than davidson.

Why does everyone use CG diagonalization first thing when they have the slightest problem? (It is a serious question, if it is in some tutorial somewhere that tutorial needs to be corrected!)



--
Dr. Lorenzo Paulatto
IdR @ IMPMC -- CNRS & Université Paris 6
phone: +33 (0)1 442 79822 / skype: paulatz
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