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Re: [abinit-forum] Negative phonon frequencies

From: NISHIMATSU Takeshi <t_nissie@yahoo.co.jp>
To: forum@abinit.org
Subject: Re: [abinit-forum] Negative phonon frequencies
Date: Mon, 13 Oct 2008 07:32:13 +0900 (JST)
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Mozhgan,

> I have done response function1 for PbTiO3 and at the end some of my acoustic
> phonon frequencies were negative. In spite of the ferroelectricity of
> PbTiO3,
> is it a reasonable thing(soft mode)? If not, what should I do? can I solve
> it
> maybe by increasing the number of nband?

nband=22=(14+12+3*6)/2=(half of the number of valence electrons) is OK.
You need the enough number of k-points (8x8x8), the enough large cutoff
energy for PW, and the enough large nstep.

Good luck,
-- Takeshi
love && peace && free_software

[abinit-forum] Negative phonon frequencies, mozhganamini, 10/12/2008
- Re: [abinit-forum] Negative phonon frequencies, NISHIMATSU Takeshi, 10/13/2008
- Re: [abinit-forum] Negative phonon frequencies, ธนูสิทธิ์ บุรินทร์ประโคน, 10/13/2008