DFT-D4: Difference between revisions

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DFT-D4 is an external package maintained by the Grimme group that can be [[Makefile.include#DFT-D4_.28optional.29|linked to VASP]].
DFT-D4 is an external package maintained by the Grimme group that can be [[Makefile.include#DFT-D4_.28optional.29|linked to VASP]].
Read the [https://dftd4.readthedocs.io/en/latest/ documentation] for more information about this package.
Read the [https://dftd4.readthedocs.io/en/latest/ documentation] for more information about this package.
DFT-D4 adds [[:Category:Van der Waals functionals|van-der-Waals (vdW) interactions]] to DFT because they are not included in most exchange-correlation functionals.
It approximates the vdW interactions considering only the structure of the system which allows for a fast computation.
Since every functional has different interactions between atoms, DFT-D4 tailors its adjustable parameters to the functional.


== Usage ==
== Usage ==


In general, VASP passes the used exchange-correlation functional to DFT-D4.
In most cases, it is sufficient to set {{TAG|IVDW}}=13 in the {{FILE|INCAR}} file if VASP was [[Makefile.include#DFT-D4_.28optional.29|compiled and linked to DFT-D4]].
DFT-D4 decides on the optimal choice of parameters for the specific functional.
Internally, VASP passes the name of the used exchange-correlation functional to DFT-D4.
Typically, you do not need to modify the parameters of the interaction.
Subsequently, DFT-D4 maps this name of the functional to optimized settings for the adjustable parameters of the vdW interaction.
If you want to or if DFT-D4 does not implement specific parameters for the functional,
VASP uses these parameters to compute the DFT-D4 energies, forces, and stresses in every ionic step and adds them to the corresponding DFT terms.
set the following parameters in the {{FILE|INCAR}} file:
As a result, you can relax structures or run [[MD|MD simulations]] with an approximate treatment of vdW interactions.
{{NB|warning|Below, we explain how to tweak the parameters of DFT-D4. Typically, you should not modify them unless you have a very good reason, e.g., because the interface is not implemented for the exchange-correlation functional you use.}}
 
VASP allows setting the following tags in the {{FILE|INCAR}} file to change the strength of the vdW interaction.


* {{TAG|VDW_S6}}, {{TAG|VDW_S8}} determine the strength of the dipole-dipole and dipole-quadrupole interaction.
* {{TAG|VDW_S6}}, {{TAG|VDW_S8}} determine the strength of the dipole-dipole and dipole-quadrupole interaction.
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== Related tags and articles ==
== Related tags and articles ==
{{TAG|IVDW}},
{{TAG|VDW_S6}},
{{TAG|VDW_S6}},
{{TAG|VDW_S8}},
{{TAG|VDW_S8}},
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[[Makefile.include#DFT-D4_.28optional.29|Linking to DFT-D4]]
[[Makefile.include#DFT-D4_.28optional.29|Linking to DFT-D4]]


[[Category:Exchange-correlation functionals]][[Category:Van der Waals functionals]]
[[Category:Exchange-correlation functionals]][[Category:Van der Waals functionals]][[Category:Howto]]

Latest revision as of 10:39, 14 June 2024

DFT-D4 is an external package maintained by the Grimme group that can be linked to VASP. Read the documentation for more information about this package. DFT-D4 adds van-der-Waals (vdW) interactions to DFT because they are not included in most exchange-correlation functionals. It approximates the vdW interactions considering only the structure of the system which allows for a fast computation. Since every functional has different interactions between atoms, DFT-D4 tailors its adjustable parameters to the functional.

Usage

In most cases, it is sufficient to set IVDW=13 in the INCAR file if VASP was compiled and linked to DFT-D4. Internally, VASP passes the name of the used exchange-correlation functional to DFT-D4. Subsequently, DFT-D4 maps this name of the functional to optimized settings for the adjustable parameters of the vdW interaction. VASP uses these parameters to compute the DFT-D4 energies, forces, and stresses in every ionic step and adds them to the corresponding DFT terms. As a result, you can relax structures or run MD simulations with an approximate treatment of vdW interactions.

Warning: Below, we explain how to tweak the parameters of DFT-D4. Typically, you should not modify them unless you have a very good reason, e.g., because the interface is not implemented for the exchange-correlation functional you use.

VASP allows setting the following tags in the INCAR file to change the strength of the vdW interaction.

  • VDW_S6, VDW_S8 determine the strength of the dipole-dipole and dipole-quadrupole interaction.
  • VDW_A1, VDW_A2 are scaling constants in the Becke-Johnson damping.

For more information regarding these parameters, please refer to the DFT-D4 paper.[1]

References

Related tags and articles

IVDW, VDW_S6, VDW_S8, VDW_A1, VDW_A2, DFT-D3, Linking to DFT-D4