[Wien] Spontaneous polarization with Berry phase method

[Oleg Rubel]

Dear Mostefa,

I run your structure file under LSDA and it turned out to be metallic 
(please see below). Is this what you have too?

Oleg


+++++++++++++ last iteration form BiCoO3.scf +++++++++++++
:KPT   :      NUMBER OF K-POINTS:    40
:GAP  : -99999.   Ry = -9999.    eV  ( metallic )
          Bandranges (emin - emax) and occupancy:
:BAN00015:  15    0.055488    0.165506  2.00000000
:BAN00016:  16    0.113749    0.200816  2.00000000
:BAN00017:  17    0.131335    0.241349  2.00000000
:BAN00018:  18    0.183033    0.246160  2.00000000
:BAN00019:  19    0.191768    0.282319  2.00000000
:BAN00020:  20    0.201936    0.291997  2.00000000
:BAN00021:  21    0.272125    0.370843  2.00000000
:BAN00022:  22    0.415842    0.453655  2.00000000
:BAN00023:  23    0.440536    0.521746  1.98029924
:BAN00024:  24    0.448050    0.530518  1.59519522
:BAN00025:  25    0.448050    0.537939  0.42450554
:BAN00026:  26    0.523239    0.591985  0.00000000
:BAN00027:  27    0.606905    0.821999  0.00000000
:BAN00028:  28    0.770780    0.897447  0.00000000
:BAN00029:  29    0.823424    0.897447  0.00000000
:BAN00030:  30    0.936794    1.203061  0.00000000
         Energy to separate low and high energystates:   -0.07844


:NOE  : NUMBER OF ELECTRONS          =  48.000

:FER  : F E R M I - ENERGY(TETRAH.M.)=   0.5066195849
:GMA  : POTENTIAL AND CHARGE CUT-OFF  12.00 Ry**.5



On 01/11/2013 12:58 PM, mostefa djermouni wrote:
> Dear Oleg Rubel,
>
> I have calculated the spontaneous polarization for BiCoO3 in tetragonal
> structure, and then,
> I have got different results between [0 - 2] range and [-1 - +1] range.
>
> Please I have some questions:
>
> - What is the significance of negative values of total polarization ?
> - Why the values of P_x and P_y is not  ~0 ?
> - Is my calculation is true ?
>
> Please find in attached files the BiCoO3.struct, BiCoO3.berrypi (for
> non-centrosymmery case) and
> BiCoO3.berrypi (for centrosymmery case).
>
> NB: the spontaneous polarization of BiCoO3 in literature is: 179 uCm/
>
> Thanks in advance.
>
> -------------------------------------------------------
> Mostefa DJERMOUNI
> Modeling and Simulation in Materials Science Laboratory
> University of Sidi Bel-Abbes
> 22000 Sidi Bel-Abbes, Algeria
> Tel: +213 795 626 105
> -------------------------------------------------------
>
>
>
>
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-- 
Oleg Rubel, PhD
Scientist, Thunder Bay Regional Research Institute
Adjunct Professor, Dept Physics, Lakehead University
290 Munro St, Thunder Bay, P7A 7T1, Ontario, Canada
Phone: +1-807-7663350
Fax: +1-807-3441948
E-mail: orubel at lakeheadu.ca
Homepage: http://www.tbrri.com/~orubel/