[Pw_forum] metallic BP?

giacsport at libero.it giacsport at libero.it
Sat Dec 3 09:39:37 CET 2011


         Hi Eric,                      sorry. I expressed my point maybe in a misleading way...I mean, i found a gap metallic (Homo is highest in energy than Lumo) but the system is reported to be a wide bandgap semiconductor (Gap > 2. eV)"highest occupied, lowest unoccupied level (ev):     6.1092    5.4104"HOMO=6.109  LUMO=5.4104  (as far as I understand)....the gap is 0.7 eV only if you switch HOMO and LUMO
The structure is the experimental one I found from a previous paper and it was optimized with Gaussian PBC

Thanks,G
                      


----Messaggio originale----

Da: germaneau at gucas.ac.cn

Data: 03/12/2011 16.32

A: "giacsport at libero.it"<giacsport at libero.it>, "PWSCF Forum"<pw_forum at pwscf.org>

Ogg: Re: [Pw_forum] metallic BP?




  
  
    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

_______________________________________________
Pw_forum mailing list
Pw_forum at pwscf.org
http://www.democritos.it/mailman/listinfo/pw_forum


    
    

    -- 

      
        
          
            Be the change you wish to see in the world

          
          
            
              — Mahatma Gandhi —

            
          
          

          Dr.
            Éric Germaneau

          

          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

                Why? See: http://www.gnu.org/philosophy/no-word-attachments.html
                
              
            
          
      
        
  





-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20111203/efd48493/attachment.html>


More information about the users mailing list