Graphite TS binding energy

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Task

Determine the interlayer binding energy of graphite in its experimental structure using the method of Tchatchenko and Scheffler to account for van der Waals interactions.

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Input

POSCAR

• Graphite:

graphite
1.0
1.22800000 -2.12695839  0.00000000
1.22800000  2.12695839  0.00000000
0.00000000  0.00000000  6.71
4
direct
   0.00000000  0.00000000  0.25000000
   0.00000000  0.00000000  0.75000000
   0.33333333  0.66666667  0.25000000
   0.66666667  0.33333333  0.75000000

• Graphene:

graphite
1.0
1.22800000 -2.12695839  0.00000000
1.22800000  2.12695839  0.00000000
0.00000000  0.00000000  20.
2
direct
   0.00000000  0.00000000  0.25000000
   0.33333333  0.66666667  0.25000000

INCAR

IVDW=20            
LVDW_EWALD =.TRUE. 
NSW=1 
IBRION=2
ISIF=4
PREC=Accurate
EDIFFG=1e-5
LWAVE=.FALSE.
LCHARG=.FALSE.
ISMEAR=-5
SIGMA  =   0.01
EDIFF=1e-6
ALGO=Fast
NPAR=2

KPOINTS

• Graphite:

Monkhorst Pack
0
gamma
16 16 8
0 0 0

• Graphene:

Monkhorst Pack
0
gamma
16 16 1
0 0 0

There is no interaction of layers in z-direction for graphene so we need only 1 k point in this direction.

Calculation

Semilocal DFT at the GGA level underestimates long-range dispersion interactions. In the case of graphite, PBE predicts the interlayer binding energy of ~1 meV/atom which is too small compared to the RPA reference of 0.048 eV/atom (Lebgue et al., PRL 105, 195401 (2010)).

In this example, the interlayer binding energy of graphite in its experimental structure is determined using the Tkatchenko-Scheffler method, which performs well in description of the structure of graphite (see e.g. example graphite interlayer distance).

The calculation is performed in two steps (sigle-point calculations) in which the energy for bulk graphite and for graphene are obtained. The binding energy is computed automatically and it is written in the file results.dat.

Even though the TS method predicts a reasonable geometry it overestimates the energetics strongly: the computed binding energy of -0.083 eV/atom is too large compared to the RPA reference of 0.048 eV/atom This overestimation is - at least in part - due to neglecting the many-body interactions (see example graphite MBD binding).

Used INCAR Tags

ALGO, EDIFF, EDIFFG, IBRION, ISIF, ISMEAR, IVDW, LCHARG, LVDW_EWALD, LWAVE, NPAR, NSW, PREC, SIGMA

Download

graphiteBinding_ts.tgz

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