21
votes
Accepted
Difference between Van der Waals (DFT-D and DFT-D3) corrections in ab-initio calculations
As you mention, there are many empirical dispersion corrections for density functional theory.
Generally, the term "DFT-D" refers to a generic dispersion-corrected density functional calculation, ...
- 9,265
15
votes
Keesom and Debye forces in DFT
In computational chemistry, the term "van der Waals interaction" tend to refer to the London term only; the Keesom term (electrostatic interactions between two freely-rotating permanent ...
- 9,621
14
votes
Are dispersion correction methods for DFT (such as D3) useful for geometry optimization?
Yes, vdW interaction affects energies but, also, geometries. This effect is the most pronounced if a DFT method predicts an interaction in a dimer to be repulsive: a geometry optimization will then ...
- 1,331
13
votes
Are dispersion correction methods for DFT (such as D3) useful for geometry optimization?
Dispersion correction DOES affect the final geometry.
The dispersion interaction is a function of geometry. A crude approximation is to write the dispersion interaction between two neutral molecules ...
- 1,124
10
votes
Accepted
SCAN-RVV10 geometry optimization
Imagine you have a (hypothetical) method that can exactly capture the van der Waals interaction. Then when you do a geometry optimization, you are neglecting the quantum and thermal fluctuations of ...
- 11k
10
votes
Are dispersion correction methods for DFT (such as D3) useful for geometry optimization?
Optimization routines typically use the negative gradient of the energy in some form to determine the displacement during an optimization step and the dispersion correction changes the energy, which ...
- 941
9
votes
What are the different ways of calculating dispersion constants?
2007 (Becke & Johnson): XDM
XDM stands for "exchange-hole dipole moment" which is a model introduced by Becke and Johnson in 2007 for calculating dispersion constants. The formulas are ...
8
votes
Accepted
Calculation of dispersion energies for organometallic complexes with Gaussian
Van der Waal's radii for all atoms in the molecule are required to compute the dispersion for $\omega$B97X-D (this is also true for Grimme's dispersion). Unfortunately, Gaussian09 doesn't seem to have ...
- 15.5k
7
votes
Band structure with additive dispersion methods
It doesn't matter. The self-consistent calculation will use the Hamiltonian constructed from the relaxed structure, in which the D3 has been applied and should not be considered again.
Take bilayer ...
- 15.1k
7
votes
Are dispersion correction methods for DFT (such as D3) useful for geometry optimization?
tldr; Use dispersion correction for optimization
I asked a very similar question a few years ago. Many indications for dispersion corrections in density functional methods are for intermolecular ...
- 9,265
7
votes
Accepted
DFT-D2 calculations in VASP and Gaussian
The error due to the basis set will likely be larger than any difference in the DFT-D2 treatment. This is because you cannot use the same basis set in a (non-periodic) Gaussian calculation and a VASP ...
- 9,621
6
votes
Accepted
Choosing the right basis set for describing vdW-interactions with DFT-D3
If you use DFT-D3, vdW interactions are already included in the empirical dispersion correction.
The general guidelines for choosing basis sets apply: use modern families of consistent basis sets. For ...
- 19.1k
6
votes
Accepted
How might inclusion of a Grimme dispersion correction influence a simulation of a dense liquid that is not water?
Following Tyberius's suggestion, I now turn my comment into an answer.
As always, the most reliable way of estimating the effect of the dispersion correction is to actually do two simulations, one ...
- 9,621
6
votes
Accepted
Are dispersion constant calculated differently for elements that are heavier than Xe?
There's many ways to calculate a $C_6$ value, for which it doesn't matter whether the element is heavier or lighter than Xe.
One of the simplest equations for $C_6$ is in the abstract of a 1931 paper ...
5
votes
Accepted
Should I add vdW interaction to estimate chemical potential of metallic elements?
Short version
If the $\text{LiCoO}_2$ is computed with van der Waals included, so should everything else.
Long version
This seems more of a thermodynamics question than a simulations question given ...
- 965
5
votes
What are the different ways of calculating dispersion constants?
2009 (Tkatchenko−Scheffler) TS
The Tkatchenko−Scheffler model for van der Waals interactions (vdW) defines the $C_6^{AB}$ parameters in an ab-initio fashion. In TS model the vdW energy $E_{vdw}$ is ...
- 2,292
5
votes
Band structure with additive dispersion methods
A PBE vs PBE+D3 calculation will have the same band structure if the same geometry is used. If the geometry is optimized, however, they can differ but the D3 correction does not directly influence ...
- 11k
4
votes
For what DFT functional is useless to add D3 or similar corrections?
You should not apply empirical dispersion corrections to functionals that are overbinding already without dispersion. LDA functionals are a prominent example: even LDA exchange is overbinding by ...
- 19.1k
3
votes
Dispersion correction and band structure
@Xivi76 is correct. Dispersion corrections have no direct influence on the band structure. As such, there is no need to add the D3 correction on your HSE06 static calculation if you're only interested ...
- 7,361
3
votes
Accepted
Best vdW correction functional for transition metal dichalcogenides
DFT-D2 is simple and reliable. I've used DFT-D2 for most of my worked on 2D materials but I do I have to caution you that I have not specifically work on TMGs. You can test out the results you obtain ...
- 2,392
3
votes
How to obtain imaginary frequency polarizability?
I dedicate this answer to Bob Le Roy and Jim Mitroy who passed away in August 2018 and August 2014 respectively. I was thinking about them a lot while writing this answer.
Dynamic dipole ...
3
votes
Accepted
Does the relaxed density (and therefore the relaxed orbitals) depend on the final energy in OO-DHDF+D calculations?
The DFT-D family of corrections, including DFT-D2, DFT-D3 and DFT-D4, are energy corrections that depend on the atomic coordinates but not the wavefunction. (The DFT-D4 energy does depend on atomic ...
- 9,621
3
votes
Are dispersion constant calculated differently for elements that are heavier than Xe?
You already have a potentially good answer from Nike Dattani, however I might frame this as an entirely different question. Unless you have a good reason to determine you own dispersion constants / ...
- 11k
2
votes
Electronic Convergence Issues with Nonlocal vdW-DF Functionals (in VASP)
I've managed to converge my optB88-vdW geometry relaxations to within forces of 0.002 eV/Å (EDIFFG=0.002), with an electronic convergence tolerance of $10^{-6}$ eV (...
- 1,256
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