[Pw_forum] About graphene nanoribbon input.

[Pablo Álvarez Zapatero]

Hi everyone,


I am trying to calculate thermal conductivity of a graphene nanoribbon throught other program called "phono3py", which uses QE to perform ab initio calculations. Then, in order to understand and validating my results, i am currently trying to calculate the phonon bands of a different sized graphene nanoribbon, using the so called phonopy.

Firstly, i succesfully solved the infinite (phonon bands) grapehene system with phonopy+QE. Now, I have looked for propper inputs in QE forums for a nanorribon, but i do not know if the input i am using is well posed. Using a single gamma k point (as i read in this forum), results are ridicolous. Now, using these k-points it lasts for 24 hours for a sigle .in calculation (there are 11 more in a band calculation).


&control
 calculation = 'scf'
 prefix='grapheneph',
 tprnfor = .true.
 tstress = .true.
 pseudo_dir = './',
 outdir='./saleph51/'
/
&system
 ibrav = 0,
 nat = 84,
 ntyp = 1,
 occupations = 'smearing'
 smearing = 'm-p'
 degauss = 0.01
 ecutwfc = 30.0,
 ecutrho = 150.0,
/
&electrons
    mixing_beta= 0.7
    conv_thr = 1.0d-8
    diagonalization = 'david'
    mixing_mode = 'plain'
/
K_POINTS automatic
12 12 1 0 0 0
!    ibrav = 0, nat = 84, ntyp = 1
CELL_PARAMETERS bohr
   29.8200000000000003    0.0000000000000000    0.0000000000000000
    0.0000000000000000   16.1490000000000009    0.0000000000000000
    0.0000000000000000    0.0000000000000000   10.0000000000000000
ATOMIC_SPECIES
  C   12.01070   C.pbe-rrkjus.UPF
ATOMIC_POSITIONS crystal

[...]



I read that is convenient to use a multiple of 3 k-point mesh to achieve better results in any direction (i read for instance 12 or even 60!). Since my system is flat, i set that k-point mesh in x-y.



So the question is, is this input fine? Do will solve the energy problem (DFT ) accurately?


Thank you for your time and patience!

Pablo.
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