Grimme's DFT-D2 semi-empirical model for van der Waals interactions

[ams_nanolab]

Yes I understand, but where to find the values for Mo, W etc. transition metals ? Could you point. Are there any theoretical formula?

[Anders Blom]

Turns out that if you (or rather, we!) read Grimme's article a bit closer, the same parameters apply to the whole list of elements from Y to Cd, so you can use that value for Mo. Presumably this is an approximation, but so is the whole approach anyway.

Thus, add, in the relevant places,

PeriodicTable.Mo :  1.606*Angstrom,

PeriodicTable.Mo : 24.67*C6_unit,

and try that. There are already parameters for S in the script.

For W (tungsten) it seems there are no parameters at least in Grimme's article - there are no parameters above Xe. Perhaps they have been published elsewhere, you can try to search for it.

[ams_nanolab]

Thanks it is working now, will look for W database, if found will post it. 

[marmotte]

Dear Anders,

Could you please tell me if the D2-DFT approach will be in the final version 13.8 ? I mean, if we will be able to run the Geometry optimization and also extract the band structure, DOS etc.. .
By the way, could you please update us about the final version 13.8 ?

Thank you

[Anders Blom]

We will see precisely how it appears in the final version, but it will someone be part of the released package.

I must also point out that there is a bug in the version of the script above (I will actually remove it). The correct script is attached here - and it also supports calculating the stress using the Grimme additional potential.

The D2 approach can already today be used for geometry optimizations and bands structure and DOS etc (although I suspect it has a rather small influence on those quantities), using the attached script.

[Anders Blom]

The DFTD2 functionality is now available in the main NanoLanguage module, and thus you don't need any special import statements to use it. The attached file will run as-is in 13.8 (but not some of the preview versions to 13.8, like the beta-versions).

[atk_user]

Dear, Anders Blom Is it possible to calculate the Density of States (DOS) with DFT-D2 (PBE-vdW)? How about I-V calculation with DFT-D2? I tried but the DOS is the same to the results of the DFT (PBE) functional. (The geometry optimization work fine!!) Here is the part of my input file (Exchange-Correlation and DOS part)

Code

#----------------------------------------
# Exchange-Correlation
#----------------------------------------
exchange_correlation = GGA.PBE

numerical_accuracy_parameters = NumericalAccuracyParameters(
    k_point_sampling=(40, 1, 2),
    )

DFTD2LCAO = extendedCalculatorWithDFTD2(LCAOCalculator)
calculator = DFTD2LCAO(
    basis_set=basis_set,
    exchange_correlation=exchange_correlation,
    numerical_accuracy_parameters=numerical_accuracy_parameters,
    )

bulk_configuration.setCalculator(calculator)
nlprint(bulk_configuration)
bulk_configuration.update()
nlsave('analysis.nc', bulk_configuration)

# -------------------------------------------------------------
# Density of states
# -------------------------------------------------------------
density_of_states = DensityOfStates(
    configuration=bulk_configuration,
    kpoints=MonkhorstPackGrid(40,4,1),
    energy_zero_parameter=FermiLevel,
    bands_above_fermi_level=None,
    )
nlsave('analysis.nc', density_of_states)
nlprint(density_of_states)

[Anders Blom]

Why would you expect there to be a difference?