Simple-DFT-D3
Simple DFT-D3[1][2][3] is an external package that implements the DFT-D3 method[4][5] and can be linked to VASP. DFT-D3 adds to the DFT energy expression a term that accounts for the van der Waals (vdW) interactions, which are in principle not included in semilocal and hybrid exchange-correlation functionals. This is an approximation of the atom-pairwise type that depends only on the structure of the system, which allows for a fast computation. Since every functional has different interactions between atoms, DFT-D3 tailors its adjustable parameters to the functional. For more information regarding these parameters, please refer to the DFT-D3 papers[4][5] and simple DFT-D3 websites.[2][3]
Compared to the implementation in VASP of DFT-D3 (IVDW=11 and 12, see DFT-D3), the simple DFT-D3 package has some advantages:
- It offers more types of damping functions (SDFTD3_DAMPING).
- Allows to activate the three-body Axilrod–Teller–Muto term (VDW_S9).
- It has vdW parameters for elements up to lawrencium ([math]\displaystyle{ Z=103 }[/math]), while it is up to plutonium ([math]\displaystyle{ Z=94 }[/math]) in the VASP implementation.
- It is computationally faster.
| Important: The use of simple DFT-D3 with VASP is available from VASP.6.6.0 onwards that needs to be compiled with -DSDFTD3. |
Usage
For some of the common exchange-correlation functionals (e.g., PBE, SCAN, or HSE06) it is sufficient to set IVDW=15 and SDFTD3_DAMPING for the damping function in the INCAR file. Internally, VASP passes automatically the name of the functional to simple DFT-D3. However, for other functionals the SDFTD3_XC tag has to be used to specify the functional to simple DFT-D3 (the names are listed in the file param.f90 of the simple DFT-D3 source code). Subsequently, simple DFT-D3 maps the functional name to optimized settings for the adjustable parameters of the vdW interaction. VASP uses these parameters to compute the DFT-D3 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.
| Important: Below, we explain how to tweak the parameters of DFT-D3. 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:
- SDFTD3_DAMPING : type of damping function.
- SDFTD3_XC : functional name to determine the set of vdW parameters.
- VDW_S6 : scaling of the dipole-dipole dispersion.
- VDW_S8 : scaling of the dipole-quadrupole dispersion.
- VDW_SR : scaling of the dipole-dipole damping.
- VDW_SR8 : scaling of the dipole-quadrupole damping.
- 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_BETA : offset for damping radius or power for the zero-damping component
- VDW_S9 : scaling of the three-body dispersion energy.
- VDW_RADIUS : two-body interaction cutoff.
- VDW_CNRADIUS : coordination number cutoff.
References
- ↑ S. Ehlert, Simple dft-d3: library first implementation of the d3 dispersion correction, J. Open Source Softw. 9, 7169 (2024).
- ↑ a b https://dftd3.readthedocs.io
- ↑ a b https://github.com/dftd3
- ↑ a b S. Grimme, J. Antony, S. Ehrlich, and S. Krieg, J. Chem. Phys. 132, 154104 (2010).
- ↑ a b S. Grimme, S. Ehrlich, and L. Goerigk, J. Comput. Chem. 32, 1456 (2011).
Related tags and articles
IVDW, SDFTD3_DAMPING, SDFTD3_XC, VDW_S6, VDW_S8, VDW_SR, VDW_SR8, VDW_A1, VDW_A2, VDW_BETA, VDW_S9, VDW_RADIUS, VDW_CNRADIUS, DFT-D3, DFT-D4