Graphite TS binding energy: Difference between revisions
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which is too small compared to the RPA | which is too small compared to the RPA | ||
reference of 0.048 eV/atom | reference of 0.048 eV/atom | ||
<ref name="lebegue"/>. | |||
In this example, the interlayer binding energy | In this example, the interlayer binding energy | ||
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== Download == | == Download == | ||
[http://www.vasp.at/vasp-workshop/examples/graphiteBinding_ts.tgz graphiteBinding_ts.tgz] | [http://www.vasp.at/vasp-workshop/examples/graphiteBinding_ts.tgz graphiteBinding_ts.tgz] | ||
== References == | |||
<references> | |||
<ref name="lebegue">[https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.196401 S. Lebègue, J. Harl, Tim Gould, J. G. Ángyán, G. Kresse, and J. F. Dobson, Phys. Rev. Lett. 105, 196401 (2010).]</ref> | |||
</references> | |||
---- | ---- | ||
[[VASP_example_calculations|To the list of examples]] or to the [[The_VASP_Manual|main page]] | [[VASP_example_calculations|To the list of examples]] or to the [[The_VASP_Manual|main page]] | ||
[[Category:Examples]] | [[Category:Examples]] | ||
Revision as of 13:14, 10 May 2017
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.
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 [1].
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).
Download
References
To the list of examples or to the main page