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. Additionally, without the dispersion correction, the value is as low as -0.28 eV/Li. 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