[Pw_forum] Not getting right Band structure

Neel Singh neelphysics at yahoo.in
Tue Jul 28 11:54:14 CEST 2009



--- On Tue, 28/7/09, Neel Singh <neelphysics at yahoo.in> wrote:



Hi all,

 I am new to PWSCF and trying to calculate Band structure of YVO4 but facing two problems ?

1.)No band is plotted in grpah above 0.0 value. The band structure is very large  , as in the  band  Output file  it is calculated like 

 End of band structure calculation

          k = 0.0000 0.0000 0.0000     band energies (ev):

-12.5188 -12.0378 -11.9977 -11.5969 -11.2203 -11.0959 -10.5816 -10.5411
   -10.4664 -10.4588 -10.0894 -10.0558  -9.6071  -9.5783  -9.0182  -8.9833
     0.3058   0.6382   0.7747   0.9726   1.3117   1.4323   1.4740   1.5240
means band gap at gamma = 0.3058-(-8.9833)=
 8.2891
 which is very large ??

2) In the output of SCF and Bands , the output file has 4 warnings 

 warning: symmetry operation #  3 not allowed.   fractional translation:
       0.0000000 -0.5000000  0.1164604  in crystal coordinates
     warning: symmetry operation #  4 not allowed.   fractional translation:
       0.0000000  0.0000000  0.1164604  in crystal coordinates
     warning: symmetry operation # 25 not allowed.   fractional translation:
       0.0000000  0.0000000  0.1164604  in crystal coordinates
     warning: symmetry operation # 26 not allowed.   fractional translation:
       0.0000000 -0.5000000  0.1164604  in
 crystal coordinates

for this I have already increase the following quantities  in the  increments
kinetic-energy cutoff     =      40.0000  Ry to 60
     charge density cutoff     =     250.0000  Ry to 400
But still the warnings are there.

Please help me. I will be very thankful. My Inputs for the calculations are following: 

SCF INPUTS

&control
    calculation='scf',
    restart_mode='from_scratch',
    prefix='yvo'
    pseudo_dir = '/home/physics/pseudo/',
    outdir='/home/physics/work/yvo/temp'
 /
 &system
    ibrav =1, a=7.118300514, b= 7.118300514, c=6.289300454
, nat =24, ntyp= 3,  ecutwfc = 40.0,ecutrho=250,
 occupations='smearing',
 smearing='mp', degauss=0.01, 


 /
 &electrons
    mixing_beta = 0.7
    diagonalization = 'david'
    conv_thr =  1.0e-4
/
 &ions
 /

ATOMIC_SPECIES
  Y     88.90585     Y.pbe-nsp-van.UPF
  V     50.9415      V.pbe-sp-van.UPF
  O     15.9994      O.pbe-van_ak.UPF
ATOMIC_POSITIONS {angstrom}
Y             0.000000000   5.338725356    0.786162553
Y             3.559150238   1.779575118    3.930812762
Y             3.559150238  
 5.338725356    2.358487657
Y             0.000000000   1.779575118    5.503137866
V             0.000000000   1.779575118    2.358487657
V             3.559150238   5.338725356    5.503137866
V             0.000000000   5.338725356    3.930812762
V             3.559150238   1.779575118    0.786162553
O             0.000000000   3.090765987   
 1.262891534
O             3.559150238   6.649916224    4.407541744
O             3.559150238   4.027534488    4.407541744
O             0.000000000   0.468384251    1.262891534
O             5.807109607   5.338725356    2.835216639
O             4.870341106   1.779575118    5.979866849
O             3.559150238   3.090765987    1.881758675
O            
 0.000000000   6.649916224    5.026408885
O             0.000000000   4.027534488    5.026408885
O             3.559150238   0.468384251    1.881758675
O             4.870341106   5.338725356    0.30943357
O             5.807109607   1.779575118    3.45408378
O             1.311190868   1.779575118    3.45408378
O             2.247959369   5.338725356   
 0.30943357
O             2.247959369   1.779575118    5.979866849
O             1.311190868   5.338725356    2.835216639

K_POINTS {automatic}
  2 2 2 0 0 0

------------------------------------------------------------------------------------------------
                                     BANDS INPUT
---------------------------------------------------------------------------------------------------

&control
    calculation='bands'
    pseudo_dir = '/home/physics/pseudo/',
   
 outdir='/home/physics/work/yvo/temp',
    prefix='yvo',
  
 /
 &system
    ibrav =1, a=7.118300514, b= 7.118300514, c=6.289300454, nat=24, ntyp=3, 
ecutwfc = 40.0,ecutrho=250, occupations='smearing', smearing='mp', degauss=0.01, nbnd= 98, 
    
 /
 &electrons
   mixing_beta=0.7
   conv_thr=1.0e-4
 diagonalization = 'david'
/
&ions
 /

ATOMIC_SPECIES
 Y       88.90585     Y.pbe-nsp-van.UPF
  V      50.9415      V.pbe-sp-van.UPF
  O     15.9994      O.pbe-van_ak.UPF
ATOMIC_POSITIONS {angstrom}
Y             0.000000000   5.338725356   
 0.786162553
..
..
..
O  ............        

K_POINTS
 26
0.000 0.000 0.000  1
0.000 0.000 0.125  1
0.000 0.000 0.250  1
0.000 0.000 0.375  1
0.000 0.000 0.500  1                             
0.125 0.125 0.500  1                             
0.250 0.250 0.500  1                             
0.375 0.375 0.500 
 1                            
0.500 0.500 0.500  1                             
0.500 0.500 0.333  1                             
0.500 0.500 0.166  1                             
0.500 0.500 0.000  1                             
0.375
 0.375 0.000  1                             
0.250 0.250 0.000  1                             
0.125 0.125 0.000  1                             
0.000 0.000 0.000  1                             
0.000 0.000 0.166 
 1                            
0.000 0.000 0.333  1                             
0.000 0.166 0.500  1                           
0.000 0.333 0.500  1                            
0.000 0.500 0.500  1                             
0.000 0.500 0.333 
 1                             
0.000 0.500 0.166  1                             
0.000 0.500 0.000  1                             
0.000 0.333 0.000  1                             
0.000 0.166 0.000  1
 

---------------------------------------------------------------------------------------
-----------------------------------------------------------------------------

&inputpp
    prefix  = 'yvo'
    outdir = '/home/physics/work/yvo/temp'
    filband = 'yvobands.dat'
/

----------------------------------------------------------------------------------
-----------------------------------------------------------------------------------

yvobands.dat
-15  10
yvobands.xmgr
yvobands.ps
6.1088
1.0  6.1088

--------------------------------------------------------
-------------------------------------------------- please help . Thanks in Advance



With Regards.
Neel Singh 
University of Delhi
India,







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