[Pw_forum] metallic BP?

[Éric Germaneau]

Hey Giacomo,

Forgive my ignorance but why do you say that the "scf" calculation is a 
system that "should be" metallic ?
To me it has a band gap of .7 ev.
What do you mean by wide band gap semiconductor ?
What band gap value do you expect to get?
May be the wide band gap behavior you mention does not occur at 0K.
I guess you double checked whether your system is fully relaxed.

         Éric.

On 12/02/2011 09:20 PM, giacsport at libero.it wrote:
> Dear All,
>                   I am doing calculations on a 2 atom primitive cell of Boron
> Phosphide. What I obtain from the "scf" calculation is a system that "should
> be" metallic.... Indeed
>
>       "highest occupied, lowest unoccupied level (ev):     6.1092
> 5.4104"                 -->( As far as I understand, Homo lies 0.7 eV above the
> LUMO)
>
> but of course this system is a wide-gap semiconductor.
> I am not able to figure out the reason for such behaviour. I have tested the
> same system (rhombohedral cell, a=b=c=6.06 Bohr, alpha=beta=gamma=60deg) in
> several machines finding always the same result. I attach the input file and
> the header of the two pseudos (USPP/GGA) I am using.
> Thanks in advance for any comments.
> My best,
> Giacomo
>
>
>
>
>
>
> &control
>      calculation = 'scf'
>      restart_mode='from_scratch',
>      prefix='BP',
>      tprnfor     = .true.,
>      tstress     = .true.,
>      wf_collect=.true.,
>      pseudo_dir='/home/giacomo/GGA/',
>      outdir='/home/giacomo/GGA/'
>   /
> &system
>      ibrav=  4, celldm(1) =6.061296108, celldm(3)=1,
>      nat=  2, ntyp= 2,
>      ecutwfc =50.,  nbnd = 50,
>   /
> &electrons
>      diagonalization='david'
>      mixing_mode = 'plain'
>      mixing_beta = 0.7
>      conv_thr =  1.0d-8
>   /
> ATOMIC_SPECIES
>   B  10.811     B.UPF
>   P  30.974     P.UPF
> ATOMIC_POSITIONS (crystal)
>   B  0.0  0.0  0.0
>   P  0.25000  0.25000  0.250000
> K_POINTS (automatic)
> 6 6 6 0 0 0
>
>
>
>
>
>
>
>
> For BORON:
>
> <PP_INFO>
> Generated using Vanderbilt code, version   7  3  5
> Author: unknown    Generation date:   20    6 2004
> Automatically converted from original format
>      0        The Pseudo was generated with a Non-Relativistic Calculation
>    1.00000000000E+00    Local Potential cutoff radius
> nl pn  l   occ               Rcut            Rcut US             E pseu
> 2S  2  0  2.00     10.00000000000      1.50000000000     -0.69693392995
> 2P  2  1  1.00     10.00000000000      1.53000000000     -0.26855658626
> </PP_INFO>
>
>
> <PP_HEADER>
>     0                   Version Number
>    B                    Element
>     US                  Ultrasoft pseudopotential
>      T                  Nonlinear Core Correction
>   SLA  PW   GGX  GGC    PW91 Exchange-Correlation functional
>      3.00000000000      Z valence
>     -5.70038942945      Total energy
>    0.0000000  0.0000000 Suggested cutoff for wfc and rho
>      1                  Max angular momentum component
>    781                  Number of points in mesh
>      2    4             Number of Wavefunctions, Number of Projectors
>   Wavefunctions         nl  l   occ
>                         2S  0  2.00
>                         2P  1  1.00
> </PP_HEADER>
> ---------------------------------
>
>
>
> For PHOSPHORUS
>
> <PP_INFO>
> Generated using Vanderbilt code, version   7  3  5
> Author: unknown    Generation date:   20    6 2004
> Automatically converted from original format
>      1        The Pseudo was generated with a Scalar-Relativistic Calculation
>    1.60000000000E+00    Local Potential cutoff radius
> nl pn  l   occ               Rcut            Rcut US             E pseu
> 3S  3  0  2.00     10.00000000000      1.70000000000     -1.03015496458
> 3P  3  1  3.00     10.00000000000      1.70000000000     -0.40774343239
> </PP_INFO>
>
>
> <PP_HEADER>
>     0                   Version Number
>    P                    Element
>     US                  Ultrasoft pseudopotential
>      T                  Nonlinear Core Correction
>   SLA  PW   GGX  GGC    PW91 Exchange-Correlation functional
>      5.00000000000      Z valence
>    -17.57767183737      Total energy
>    0.0000000  0.0000000 Suggested cutoff for wfc and rho
>      2                  Max angular momentum component
>    903                  Number of points in mesh
>      2    5             Number of Wavefunctions, Number of Projectors
>   Wavefunctions         nl  l   occ
>                         3S  0  2.00
>                         3P  1  3.00
> </PP_HEADER>
>
>
>
> ------------------------------------------
> Giacomo Giorgi
>
> Department of Chemical System Engineering,
> School of Engineering, The University of Tokyo
> 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
>
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-- 
/Be the change you wish to see in the world
/ --- Mahatma Gandhi ---

Dr. Éric Germaneau 
<http://www.linkedin.com/pub/%C3%A9ric-germaneau/30/931/986>

Graduate University of Chinese Academy of Sciences
College of Physical Sciences
Yuquan Road 19A
Beijing 100049
China

/Please, if possible, don't send me MS Word or PowerPoint attachments
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