[Pw_forum] Born effective charge

[Eyvaz Isaev]

Dear Mohaddeseh,

Well, let us calculate total number of valence electrons for TiO2:
12+2*6=24, thus, total number of completely filled bands is 24/2=12, not 16, if CaF2-type TiO2 is semiconducting (as I can see from my 3-years old calculations, indeed, it is semiconducting). So, you included several conduction bands in your calculations that caused NAN (not NaN, pay attention). 

ecutwfc seems to be high, and ecutrho seems to be extremely large. Usually (for US-type PsP) ecutwfc 30-35 (Ry), rarely 40Ry, and ecutrho = (8 - 12) x ecutwfc. Though, you can perform some tests for yourself to find reliable ecutwfc and ecutrho. 

CaF2-type TiO2 is quite unstable phase (at least at T=0K) even up to quite high pressure range, if you like to know. 
   
Bests,
Eyvaz.

-------------------------------------------------------------------
Prof. Eyvaz Isaev, 
Theoretical Physics Department, Moscow State Institute of Steel & Alloys, Russia, 
Department of Physics, Chemistry, and Biology (IFM), Linkoping University, Sweden 
Condensed Matter Theory Group, Uppsala University, Sweden 
Eyvaz.Isaev at fysik.uu.se, isaev at ifm.liu.se, eyvaz_isaev at yahoo.com


--- On Wed, 12/2/09, mohaddeseh abbasnejad <m.abbasnejad at gmail.com> wrote:

> From: mohaddeseh abbasnejad <m.abbasnejad at gmail.com>
> Subject: Re: [Pw_forum] Born effective charge
> To: "PWSCF Forum" <pw_forum at pwscf.org>
> Date: Wednesday, December 2, 2009, 10:23 PM
> Dear Prof. Baroni,
>  
> You are completely right.
> Here are the input files for Phonon calculation as an
> attachment.
> Yours,
> M. Abbasnejad
>  
> 
> 
>  
> On Wed, Dec 2, 2009 at 10:18 PM,
> Stefano Baroni <baroni at sissa.it>
> wrote:
> 
> 
> How can we know if you
> do not provide any details on your input files? SB 
> 
> 
> 
> 
> 
> 
> On Dec 2, 2009, at 9:41 AM, mohaddeseh abbasnejad
> wrote:
> 
> 
> 
> 
> 
> Hi,
>  
> Trying to calculate the born effective charges of my
> case, I get NAN. The structure has been relaxed
> carefully..
> What may cause the problem?
> Thanks for any comment.
>  
> Yours,
> M. Abbasnejad
> University of Tehran
> 
> -- 
> ---------------------------------------------------------
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> Mohaddeseh Abbasnejad, 
> Room No. 323, Department of Physics, 
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> 
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> ---
> Stefano Baroni -
> SISSA  &  DEMOCRITOS National
> Simulation Center - Trieste
> 
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> -- 
> ---------------------------------------------------------
> 
> Mohaddeseh Abbasnejad, 
> Room No. 323, Department of Physics, 
> University of Tehran, North Karegar Ave.,
> 
> Tehran, P.O. Box: 14395-547- IRAN 
> Tel. No.: +98 21 6111 8634  & Fax No.: +98 21 8800
> 4781
> Cellphone: +989177317514
> E-Mail:     m.abbasnejad at gmail.com
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