DFT-D4
DFT-D4 is an external package 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.
For more information regarding these parameters, please refer to the DFT-D4 paper.[1]
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 vdW parameters used in DFT-D4.
- DFTD4_MODEL : Dispersion model (available from VASP.6.6.0 onwards).
- DFTD4_XC : Functional name to determine the set of vdW parameters (available from VASP.6.6.0 onwards).
- VDW_S6 : Scaling of the dipole-dipole dispersion.
- VDW_S8 : Scaling of the dipole-quadrupole dispersion.
- VDW_A1 : Scaling of the critical radii in the Becke-Johnson rational damping.
- VDW_A2 : Offset of the critical radii in the Becke-Johnson rational damping.
- VDW_S9 : Scaling of the three-body dispersion energy (available from VASP.6.6.0 onwards).
- VDW_RADIUS : two-body interaction cutoff (available from VASP.6.6.0 onwards).
- VDW_CNRADIUS : coordination number cutoff (available from VASP.6.6.0 onwards).
References
- ↑ Template loop detected: Template:CiteTemplate loop detected: Template:CiteTemplate loop detected: Template:Cite E. Caldeweyher, J.-M. Mewes, S. Ehlert, and S. Grimme, Extension and evaluation of the D4 London-dispersion model for periodic systems, Phys. Chem. Chem. Phys. 22, 8499 (2020).
Related tags and articles
IVDW, DFTD4_MODEL, DFTD4_XC, VDW_S6, VDW_S8, VDW_A1, VDW_A2, VDW_RADIUS, VDW_CNRADIUS, DFT-D3, simple DFT-D3, Linking to DFT-D4