[Pw_forum] flat band structure

[Zeina Al-Dolami]

Dear Pwscf's developers and users,
I have started using quantum espresso recently for my research that focuses
on investigating the mechanical and electrical properties of carbon based
materials. I ran several examples of wannier90-1.2 to gain more
understanding and insight of what I need to consider when
running simulations for quantum conductance. However, I have realized that
I need to reproduce the band structures of carbon based materials that have
been already published then move to using wannier90. I came across this
paper
http://scitation.aip.org/content/aip/proceeding/aipcp/10.1063/1.3469647
page242. It is basically a linear chain of 5 carbon atoms. Also, Accelrys
Software, DMol programme, was used in this paper.  I used the below scf and
band files to reproduce the same band structure. However, the band
structure that was produced contains flat bands only. I went through the
pw-forum to find whether there was similar question or not. I found some
discussions related to band structure and other suggestions that I have
considered but no success, such as
http://qe-forge.org/pipermail/pw_forum/2005-December/078012.html . Would
you please tell me what I missed in my calculations? It is worth to mention
that I have tried to use the same parameters available in this paper in my
simulation. Any suggestion and feedback is greatly appreciated. Apologies
if my question seems trivial because I am still at the beginning and have
no background in this field. Looking forward to hearing from you. Thanks in
advance

Zeina

scf file

&CONTROL
  calculation = 'scf',
  restart_mode= 'from_scratch',
  verbosity = 'high'
  pseudo_dir  = '/pseudo',
  outdir      = './',
  prefix      = '5cc',
  tstress  = .f.,
  tprnfor  = .t.,
/
&SYSTEM
  ibrav       = 1,
!  a           = 6.520,
!  b           = 1.304,
!  c          = 1.304,
  celldm(1)   = 12.3210,
  cosbc       = 0.,
  cosac       = 0.,
  cosab       = 0.,
  nat         = 5,
  ntyp        = 1,
  ecutwfc     = 30.,
  ecutrho     = 240.,
  occupations = 'smearing',
  smearing    = 'cold',
  degauss     = 0.03,
  nspin       = 1,
/
&ELECTRONS
  mixing_beta = 0.4
  electron_maxstep = 1000,
  conv_thr    = 1.D-10,
/
ATOMIC_SPECIES
C 12.0107  C.pbe-rrkjus.UPF

ATOMIC_POSITIONS (angstrom)
C        0.183   0.000000000   0.000000000
C        1.489   0.000000000   0.000000000
C        2.791   0.000000000   0.000000000
C        4.093   0.000000000   0.000000000
C        5.399   0.000000000   0.000000000

K_POINTS {automatic}
6 1 1 0 0 0



band file
&CONTROL
  calculation = 'bands',
  restart_mode= 'from_scratch',
  verbosity = 'high'
  pseudo_dir  = '/pseudo',
  outdir      = './',
  prefix      = '5cc',
  tstress  = .f.,
  tprnfor  = .t.,
/
&SYSTEM
  ibrav       = 1,
!  a           = 6.520,
!  b           = 1.304,
!  c          = 1.304,
  celldm(1)   = 12.3210,
  cosbc       = 0.,
  cosac       = 0.,
  cosab       = 0.,
  nat         = 5,
  ntyp        = 1,
  ecutwfc     = 30.,
  ecutrho     = 240.,
  occupations = 'smearing',
  smearing    = 'cold',
  degauss     = 0.03,
  nspin       = 1,
/
&ELECTRONS
  mixing_beta = 0.4
  electron_maxstep = 1000,
  conv_thr    = 1.D-10,
! diag_full_acc = .true.

/
ATOMIC_SPECIES
C 12.0107  C.pbe-rrkjus.UPF

ATOMIC_POSITIONS (angstrom)
C        0.183   0.000000000   0.000000000
C        1.489   0.000000000   0.000000000
C        2.791   0.000000000   0.000000000
C        4.093   0.000000000   0.000000000
C        5.399   0.000000000   0.000000000

K_POINTS {crystal}
6
0.00000000  0.00000000  0.00000000  1.00000000
0.16666667  0.00000000  0.00000000  1.00000000
0.33333333  0.00000000  0.00000000  1.00000000
0.50000000  0.00000000  0.00000000  1.00000000
0.66666667  0.00000000  0.00000000  1.00000000
0.83333333  0.00000000  0.00000000  1.00000000


-- 
Zeina Al-Dolami
PhD Candidate
Microelectronics and Photonics Graduate Program
University of Arkansas
Fayetteville, AR 72701
Office: PHYS 244
Email: zaldolam at email.uark.edu <cxm075 at email.uark.edu>
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