[Pw_forum] Bad energetic of Li adsorbed graphene by DFT-D2 using QE

[Saif Ullah]

Dear QE users,

I'm trying to reproduce the Li adsorbed graphene with DFT-D2 using QE. The
adsorption energy is very much underestimated (-0.66 eV/Li) as compared to
the values found in the literature. My SIESTA vdW-DF/DZP value is -1.11
eV/Li, pretty much in agreement with the literature. I have used different
cutoff values with different pseudopotentials. I don't know where is the
problem. Following is one of my inputs. Need your suggestions, please.
Thanks

&CONTROL
   calculation='vc-relax',
  outdir='.',
  prefix='calc',
  pseudo_dir='.',
  verbosity='high',
 tstress=.true.
tprnfor=.true.
etot_conv_thr=1.0D-4
forc_conv_thr=1.D-3
wf_collect=.true.
nstep=1000
/

&SYSTEM
  ibrav=0,
  nat=51,
  ntyp=2,
  ecutwfc=40,
  ecutrho=320,
   input_dft='PBE',
  occupations='smearing',
  smearing='mp',
  degauss=0.01d0,
 vdw_corr='Grimme-D2',
!  nspin=2,
!  starting_magnetization(1)=0.7
!  starting_magnetization(2)=0.6
/

&ELECTRONS
   diagonalization='cg',
  conv_thr=1d-08,
  mixing_mode='local-TF',
  mixing_beta=0.500d0,
 electron_maxstep=2000
/
&IONS
ion_dynamics='bfgs'
/
&CELL
   cell_dynamics = 'bfgs' ,
  cell_dofree='2Dxy'
/
ATOMIC_SPECIES
C 12.010700d0 C.pbe-van_ak.UPF
Li  6.941000d0 Li.pbe-n-van.UPF
CELL_PARAMETERS (angstrom)
  12.353060724   0.000889035  -0.201450000
  -6.175669462  10.698563666   0.201310000
  -0.000049454   0.000028549  20.000000000

ATOMIC_POSITIONS (angstrom)
C       -0.123777599   0.044352021   0.750813339
C        2.347139643   0.044536664   0.710530839
C        4.816959818   0.046608474   0.671588196
C        7.288030852   0.047974520   0.631371477
C        9.759254756   0.046949526   0.590970165
C       -1.361324273   2.182837743   0.784592128
C        1.111661447   2.176898866   0.738849472
C        3.584693057   2.183131578   0.703985603
C        6.053702309   2.186196980   0.671658550
C        8.522771292   2.186413475   0.631364175
C       -2.598243992   4.325485482   0.824910219
C       -0.131078480   4.322022349   0.764237921
C        2.354133011   4.322141066   0.723759919
C        4.821870209   4.325914119   0.703967494
C        7.288439627   4.327051393   0.671562970
C       -3.831089225   6.466525503   0.871657296
C       -1.366959478   6.470638409   0.819586551
C        1.111648295   6.474564682   0.764205441
C        3.590771165   6.470877940   0.738791095
C        6.055337825   6.467163164   0.710460311
C       -5.064123742   8.605360424   0.914570582
C       -2.595447017   8.606844025   0.871611006
C       -0.124940436   8.609595937   0.824824937
C        2.349153535   8.609719150   0.784488796
C        4.820054590   8.607291549   0.750697179
C       -0.125510159   1.469181337   0.757732918
C        2.348583973   1.469399905   0.717413261
C        4.819499832   1.472058312   0.683659878
C        7.288388407   1.473415839   0.646082581
C        9.757057163   1.472349661   0.603098319
C       -1.367183927   3.608059861   0.792700719
C        1.111411672   3.604765482   0.737260404
C        3.590550668   3.608523771   0.711920217
C        6.055141240   3.612373570   0.683651546
C        8.521773207   3.612481509   0.643390074
C       -2.598108408   5.752895502   0.838312859
C       -0.130966528   5.757101185   0.777712574
C        2.354245670   5.757343547   0.737229826
C        4.822007602   5.753541812   0.717366687
C        7.288591341   5.752608946   0.684948021
C       -3.829804361   7.892507839   0.886438561
C       -1.360854441   7.895696352   0.838263118
C        1.112121068   7.902104754   0.792620096
C        3.585162055   7.896134775   0.757637017
C        6.054187493   7.893269674   0.725270353
C        1.111459010  -0.667769729   0.725378109
C        3.582681447  -0.666400412   0.685002360
C        6.052708940  -0.664305301   0.643406933
C        8.523624623  -0.664119335   0.603107212
C       10.993446884  -0.665855193   0.564139854
Li       1.142006551   5.022080560   2.622103194
K_POINTS automatic
 6 6 1 0 0 0
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