[Wien] Suggestions on PHONON Calculation 4

[Ghosh SUDDHASATTWA]

Dear Dr.Blaha, 

Thank you 

That is exactly what I got when I plotted the force constants (far distance
f.c. are still not converged)

Thanks for the hint. 

I have now taken an 18 atom as well as 24 atom supercell. 

Let us see what happens 

 

 

 

  _____  

From: wien-bounces at zeus.theochem.tuwien.ac.at
[mailto:wien-bounces at zeus.theochem.tuwien.ac.at] On Behalf Of Peter Blaha
Sent: Thursday, February 10, 2011 6:30 PM
To: A Mailing list for WIEN2k users
Subject: Re: [Wien] Suggestions on PHONON Calculation 4

 

If your supercell contains only 12 atoms ?? it is a very small supercell.

Thus only on very few q-points the phonons will be correct, while using such
a small
cell the phonons on other q-points can be completely wrong.

When you plot the force constants, you should see that the far distance f.c.
are still not
converged (small).

No, I don't want you dsy file.

When the "sum of forces" during analyse_phonon are small for every
displacement, there
is no problem with the WIEN2k calculations.

Please read the phonon manual. It is clearly said there, that you need a
sizable supercell!

Am 10.02.2011 13:13, schrieb Ghosh SUDDHASATTWA:
> Dear Dr.Blaha,
>
> I am sorry I have posted this question before.
>
> I guess my querie may be inappropriate in the Wien2k mailing list. Still,
first I would request Prof. Blaha to kindly give me permission and help me
in sorting the issue in PHONON
> which actually is not a Wien2k problem.
>
> After I imported the case.dsy file ( forces convergence obtained with
0.005 mRy) in phonon software and incorporated the lattice parameters of the
supercell and the number of
> atoms, I applied the translational and rotational invariances, I get the
Do Report in PHONON.
>
> I get the plot of force constants and I subsequently get the phonon
dispersion. I get some imaginary frequencies which I am not sure if it is
because of the wrong choice of
> supercell size (12 atoms) or the force convergence (0.005 mRy/atom)
>
> Can you please help me in this regard?
>
> Can I send you the case.dsy for your perusal?
>
> Thank you
>
> Suddhasattwa
>
>
>
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien

--

                                       P.Blaha
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