[Pw_forum] High Ecut for Ultrasoft PPs

[Zarah Baiyee]

Dear all,

I am studying a BaFeO3 perovskite structure, and I am struggling with the
convergence, primarily the Ecut WFC convergence.

So far I have used a variety of PPs for this structure, yet cannot get a
sensible convergence for the Ecut Wfc, please see my convergence data
below:

Pseudopotentials:

*Config 1:*
 Ba  Ba.pbe-spn-rrkjus_psl.1.0.0.UPF
 Fe  Fe.pbe-spn-rrkjus_psl.1.0.0.UPF
 O   O.pbe-n-rrkjus_psl.1.0.0.UPF

Ecut Convergence:

wfc=[50.0, 60.0, 70.0, 80.0, 90.0, 100.0, 110.0]

Energy=[-407.95822783, -407.9701389, -407.97593501, -407.98115532, -
407.98307678, -407.98336097, -407.98358971, -407.98436114]

*Config 2:*

 Ba   Ba.pbe-nsp-van.UPF

 Fe  Fe.pbe-spn-rrkjus_psl.0.2.1.UPF

 O   O.pbe-n-rrkjus_psl.0.1.UPF

WFC=([30.0, 40.0, 50.0, 60.0, 70.0, 80.0, 90.0, 100.0, 110.0, 120.0])

energy = ([-445.36783430, -445.74664179, -445.82508351, -445.82904841, -
445.83336392, -445.83728481, -445.83834745, -445.83834171, -445.83853799,
-445.83894056])


I have read several papers where similar studies have been done using
Ecut_wfc as low as 40Ry which confuses me greatly.  For all calc I used
Ecut_rho=8* Ecut_wfc, with a converged K-point mesh of (8x8x8), yet I am
not sure whether there is something my input (please see below). I have ran
calcs for both spin polarised and non polarised, however this has not
changed the convergence. I would greatly appreciate an insight into whether
a convergence of 100Ry is acceptable for US pseudos?


Any help will be much appreciated.

Kind Regards,


Zarah Baiyee

PhD candiate, HKUST


 &system

    ibrav = 0, nat= 5, ntyp= 3,

    ecutwfc = 100.0, ecutrho = 800.0

    occupations='smearing', smearing='gaussian', degauss=0.02

 /

 &electrons

    diagonalization='cg'

    conv_thr = 1.0e-6

    mixing_beta=0.2

/

CELL_PARAMETERS (bohr)

7.6 0.0 0.0

 0.0 7.6 0.0

 0.0 0.0 7.6

ATOMIC_SPECIES

 Ba  137.32 Ba.pbe-nsp-van.UPF

 Fe  55.84 Fe.pbe-spn-rrkjus_psl.0.2.1.UPF

 O   15.99 O.pbe-n-rrkjus_psl.0.1.UPF

ATOMIC_POSITIONS (crystal)

 Ba 0.000000 0.000000 0.000000

 Fe 0.500000 0.500000 0.500000

 O  0.500000 0.500000 0.000000

 O  0.500000 0.000000 0.500000

 O  0.000000 0.500000 0.500000

K_POINTS (automatic)

8 8 8 0 0 0
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20140416/f7f1cdb3/attachment.html>