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["Anglade Pierre-Matthieu" <anglade@gmail.com>]

Hi,

A wrong shape for the energy versus deformation is usually the symptom
(assuming good deformation and magnitude of deformations) of
unconverged calculation. If you want to perform such calculations you
MUST have a very good abslute convergence.
In
http://anglade.googlepages.com/anglade-lecture-notes-on-abinit.pdf
You will find a sample of such kind of calculation with  explanations
about all important parameters.
And some sample results of the kind of calculation you were trying to
perform in:
http://anglade.googlepages.com/anglade-abinit-code-demonstration.pdf
You will see that a very good absloute convergence is mandatory (to
compute C' in this case ecut had to be raised to 150 Ha ...). Also It
is important to use ecutsm for instance.

I fully agree with Chol-Jun Yu that at first it looks like your ecut
at least is underconverged for Ni. I would expect something between 50
and 100 Ha to be better suited.

Best

PMA


On Wed, Feb 20, 2008 at 5:42 PM, <Stephen.Hocker@mpa.uni-stuttgart.de> wrote:
> Dear Abinit users,
>
> I'm trying to calculate the elastic constants of B2 NiAl using the serial
> version of Abinit 5.4.4, unfortunately I didn't obtain any results yet. Some
> values for the parameters in my infile must be wrong, but I have no idea
> which ones I should change.
> The calculation starting from an input file like the one for Al which is
> given in the elastic tutorial stopped with the message:
> kpgsph : BUG -
>  The variables ikg, mkmem, and mpw  must satisfy ikg<=(mkmem-1)*mpw,
>  while the arguments of the routine are
>  ikg =    3060, mkmem =      20, mpw =     159
>  Probable cause: Known error in invars1 for parallel spin-polarized case.
>  Temporary solution: Change the number of parallel processes.
>  Action : contact ABINIT group.
>
> Therefore I decided to determine the elastic constants by calculation of the
> energies of strained samples. In these calculations the total energy should
> increase parabolically with increasing strain. But it doesn't. Depending on
> the parameters it usually increases somehow, but the curve is never a
> parabola. In some cases it even decreases a little.
> These are the parameters I already tried:
> ecut (280...480 eV)
> ngkpt (2 2 2...10 10 10)
> nband/fband 65/0.0d0
> occopt 3...4
> tsmear 0.03...0.07
> I tried with different pseudopotentials (Troullier-Martins) as well, namely
> 13al.pspnc, 28ni.pspnc / 13-Al.LDA.fhi, 28-Ni.LDA.fhi,  13-Al.GGA.fhi,
> 28-Ni.GGA.fhi.
>
> What else could be wrong? Thanks for any help.
> Best regards,
> Stephen
>
> This is one of my infiles:
> acell 5.7970482729504687 5.767560060000 5.767560060000 angstrom
> ecut 480 eV
> ionmov 0
> ixc 1
> kptopt 1
> natom 16
> ngkpt 10 10 10
> nstep 15
> ntypat 2
> nband 65
> occopt 4
> tsmear 0.03
> toldfe 0.005 eV
> chkprim 0
> znucl 13 28
> typat
> 1
> 1
> 1
> 1
> 1
> 1
> 1
> 1
> 2
> 2
> 2
> 2
> 2
> 2
> 2
> 2
> xangst 0.000000 0.000000 0.000000
> 0.000000 0.000000 2.883780
> 0.000000 2.883780 0.000000
> 0.000000 2.883780 2.883780
> 2.898524 0.000000 0.000000
> 2.898524 0.000000 2.883780
> 2.898524 2.883780 0.000000
> 2.898524 2.883780 2.883780
> 1.449262 1.441890 1.441890
> 1.449262 1.441890 4.325670
> 1.449262 4.325670 1.441890
> 1.449262 4.325670 4.325670
> 4.347786 1.441890 1.441890
> 4.347786 1.441890 4.325670
> 4.347786 4.325670 1.441890
> 4.347786 4.325670 4.325670
>
>



-- 
Pierre-Matthieu Anglade