[Pw_forum] odd # of electrons in primitive cell => metal ?

[Eyvaz Isaev]

Hi, 

As you have an oxide it is not so surprising.  As an example I remember B1 NiO 
or FeO. 

You should apply,  at least,   LDA+U to get more correct bands (see 
/examples/example25). Yamboo or GW+Wannier might be another tools to fix the 
problem.

Bests,
Eyvaz.
-------------------------------------------------------------------
Prof. Eyvaz Isaev, 
Department of Physics, Chemistry, and Biology (IFM), Linkoping University, 
Sweden 

Theoretical Physics Department, Moscow State Institute of Steel & Alloys, 
Russia, 

isaev at ifm.liu.se, eyvaz_isaev at yahoo.com




________________________________
From: sonu kumar <1009ukumar at gmail.com>
To: pw_forum at pwscf.org
Sent: Mon, November 1, 2010 6:54:50 AM
Subject: [Pw_forum] odd # of electrons in primitive cell => metal ?

Dear all QE users,

My primitive unit cell contains odd # of electrons so it should be metallic.
QE code indicates the system to be metallic.

But experimentally it is an insulator with band gap ~1.2 eV.

why am i not able to get the insulating nature of the system?

IS there something wrong in the input file? or in DFT?


###################################################################
PARTs OF input n output file are:

&control
    calculation='scf',             ! relax,scf,vc-relax
    verbosity='high',
    restart_mode='from_scratch',   ! 'from_scratch',
    prefix='CuFeO2',
    !wf_collect=.true.,             
    tstress=.true.,
    tprnfor=.true.,
    etot_conv_thr=1.0D-6,       
    forc_conv_thr=1.0D-5,        
                                
    pseudo_dir = './pseudo',
    outdir='./tmp',
 /

&system
    ibrav=5,celldm(1)=11.31, 
    celldm(4)=0.8718,
    
    nat=  4,
    ntyp= 3,

    !nbnd=24,                       
    ecutwfc=40,                  
    ecutrho=400,                

    !occupations = 'smearing',   
    !degauss = 0.005D0,
    !smearing='gaussian',
    nspin=1,                      
 /

&electrons
    electron_maxstep=100,     
    mixing_mode='local-TF',     
    mixing_beta = 0.2,           
    conv_thr = 1.0d-12,          
    mixing_ndim=8,                
    diagonalization='cg',        

 /


ATOMIC_SPECIES
Cu  0.0  Cu.pbe-n-van_ak.UPF
Fe  0.0  Fe.pbe-sp-van.UPF  
O   0.0  O.pbe-rrkjus.UPF
.....
....


!!!!!!!!!!!!!!!!!!!!!! Part of ouput file !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!  

 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
     from electrons : error #         1

     stopping ...
     charge is wrong: smearing is needed
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

#####################################################################


With Kind regards,

Sonu Kumar

Phd Student
Physics Department
Indian Institute of Technology 
Delhi-110016, India
web:-http://www.iitd.ac.in/



      
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