[Pw_forum] A question about force constants calculation of Graphene nano ribbon

[Zhen Huang]

Dear Espresso users-

I am currently using the software calculating interatomic force constants. I
started with a armchair edge graphene nanoribbon of  3^0.5*bondlength width
which means two primitive unit cells of graphene are aligned along the axial
direction of ribbon and separated by (3^0.5)*bondlength. However, I found
the software failed to give some of the force constant. Attached is the
structure I am trying to study and below is the script I used for force
constants calcualtion.

SCF calcualtion
**************************************************************************************************
&control
    calculation='scf'
    restart_mode='from_scratch',
    tstress = .true.
    tprnfor = .true.
    prefix='GNR',
    pseudo_dir = '/scratch/scratch96/h/huang87/espresso-4.1.1/pseudo/',

outdir='/scratch/scratch96/h/huang87/espresso-4.1.1/ZhenCalculation/GNRTry2/'
 /
 &system
    ibrav=  0, celldm(1) =8.04, nat=  8, ntyp= 1, nbnd= 20,
    ecutwfc =16.0, occupations='smearing', smearing='marzari-vanderbilt',
    degauss=0.05

 /
 &electrons
    diagonalization='cg'
    conv_thr =  1.0d-8
    mixing_beta = 0.7
 /
ATOMIC_SPECIES
 C  12.0107  C.pz-rrkjus.UPF

CELL_PARAMETERS

7.50746269 0.00000000 0.00000000
0.00000000 2.00000000 0.00000000
0.00000000 0.00000000 1.00000000


ATOMIC_POSITIONS

 C 0.462  0.5  0.000
 C 0.538  0.5  0.000
 C 0.462  0.5  0.333
 C 0.538  0.5  0.333
 C 0.500  0.5  0.500
 C 0.577  0.5  0.500
 C 0.500  0.5  0.833
 C 0.577  0.5  0.833

K_POINTS (automatic)
 1 1 32 0 0 0
*****************************************************************************

Phonon calculation

phonons of Ti
 &inputph
  tr2_ph=1.0d-12,
  prefix='GNR',
  ldisp=.true.,
  nq1=1, nq2=1, nq3=16
  amass(1)=12.0107,

outdir='/scratch/scratch96/h/huang87/espresso-4.1.1/ZhenCalculation/GNRTry2/',
  fildyn='GNR.dyn',
 /
*************************************************************************


force constants from GNR.dyn1
***************************************************************************
  1  1
252.12788999  0.00000000   -0.00114015  0.00000000  -14.77300805  0.00000000
 -0.00114015  0.00000000  ************  0.00000000   -0.06520954  0.00000000
-14.77300805  0.00000000   -0.06520954  0.00000000  -93.03374039  0.00000000
  1  2
************  0.00000000    0.09747458  0.00000000   -1.20698824  0.00000000
 -0.01665358  0.00000000  113.56482271  0.00000000   -0.00847488  0.00000000
  5.45990614  0.00000000   -0.00244794  0.00000000  113.74430800  0.00000000
  1  3
  0.53138677  0.00000000    0.01284739  0.00000000   -0.00496088  0.00000000
  0.00078527  0.00000000    1.10083154  0.00000000   -0.00960997  0.00000000
 -0.01328205  0.00000000   -0.13249470  0.00000000   -0.93853159  0.00000000
  1  4
 -0.36705054  0.00000000    0.00166782  0.00000000    0.03803961  0.00000000
 -0.01073043  0.00000000   -0.02005837  0.00000000    0.03032361  0.00000000
 -0.33345226  0.00000000    0.12638729  0.00000000   -1.53647444  0.00000000
  1  5
 -0.36239819  0.00000000   -0.02331924  0.00000000   -0.58155909  0.00000000
 -0.03210181  0.00000000   -0.86035688  0.00000000   -0.08297313  0.00000000
  1.52018776  0.00000000    0.05112061  0.00000000    0.32584098  0.00000000

***********************************************************************
Best Regards
-------
Zhen (Alex) Huang
Ph.D. Student
Nanoscale Transport Research Group
Laboratory for Computational Methods in Emerging Technologies
Cooling Technologies Research Center
School of Mechanical Engineering
Purdue University
Tel: 765 722 1113
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