[Pw_forum] SCF calculations do not converge

[mohnish pandey]

Dear Aiyad !

Try reducing "mixing_beta"(make it ~ 0.2 to 0.5) and your "ecutwfc" is too
large.. I think 40-50 Ryd will suffice. Since you are using ultrasoft
pseudopotential your ecutrho should be atleast 8 times the ecutwfc. And the
value of the convergence threshold that you have set is too low. Make it to
~1.E-08..Try the suggestions, may be you will get rid of the convergence
problem.

On Mon, Nov 21, 2011 at 11:27 PM, IYAD AL-QASIR <iyad.ne at gmail.com> wrote:

> Hello All,
> I am trying to calculate the phonon dispersion relations and phonon
> density of states of UO2.
> Please find the attached files UO2.scf.in and UO2.ph.in
>
> The calculations assume GGA and include spin-polarized effects.
>
> There are 6 representations and nine modes. The problem I have is: When I
> run the input file UO2.ph.in, the second  representation of the second
> mode for q (-0.1666667   0.1666667  -0.1666667), the *scf **calculations
> do not converge.*
>
> Notes:
> 1- My runs assume UO2  is metallic, in fact UO2 is insulator with band gap
> of 2eV.( However, when I do the calculations using the VASP code I got very
> good result only by including the polarization effects)
> 2- In order to account for the band gap, one should implement the Hubbard
> term (LDA/GGA+U)
> 3- I tried different occupations  (smearing, tetrahedra)
> 4- I tried different starting_magnetization= 0.5, 1.0
> 5- the lattice parameter a= 10.285, is based on optimizing the structure
> and including spin-polarization effects.
>
>
> Any adivce to overcome this problem is highly welcomed.
>
> Kindest Regards,
> ______________________________
> aIYAD I. AL-QASIR, PhD
> Research Associate
>
> Department of Nuclear Engineering
> North Carolina State University
> Campus Box 7909
> 2500 Stinson Dr.
> Raleigh, NC 27695-7909
>
> _______________________________________________
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> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>
>


-- 
Regards,
MOHNISH,
-----------------------------------------------------------------
Mohnish Pandey
BTech-Mtech, IIT Kanpur
Senior Project Associate,
Department of Chemical Engineering,
IIT KANPUR, UP, INDIA
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