[Pw_forum] London Dispersion force: DFT-D2

Tue May 3 11:24:30 CEST 2016

. Can anyone enlighten me on the status of vdw functionals for spin polarised calculations?

This prl http://arxiv.org/abs/1509.03759 - nicola

Cheers,
————————————————————————
Martin P. Andersson
Associate Professor
Nano-Science Center, Department of Chemistry
University of Copenhagen, Denmark

Tel: +45 3532 0280
Mobile: +46 733 893091
E-mail: ma at nano.ku.dk<mailto:ma at nano.ku.dk>
————————————————————————

On 03 May 2016, at 10:26, Giuseppe Mattioli <giuseppe.mattioli at ism.cnr.it<mailto:giuseppe.mattioli at ism.cnr.it>> wrote:

Dear Elliot
I do not know if I understand well your questions, but I try to answer:

Could someone please assist me as to how to account for London
dispersion forces with QE or essentially how to do a DFT-D2 calculation
with the the aim of accounting for the energy contribution of dispersion
forces.

Use vdw_corr='grimme-d2'
You will find in the output the dispersion force contribution to the total energy:

!    total energy              =   -2369.89004091 Ry
    Harris-Foulkes estimate   =   -2369.89004090 Ry
    estimated scf accuracy    <       0.00000001 Ry

    The total energy is the sum of the following terms:

    one-electron contribution =  -22567.16723495 Ry
    hartree contribution      =   11423.49753189 Ry
    xc contribution           =    -757.02966668 Ry
    ewald contribution        =    9530.66102736 Ry
    Dispersion Correction     =      -0.98373910 Ry
    Hubbard energy            =       1.13399751 Ry
    smearing contrib. (-TS)   =      -0.00195694 Ry

I'm trying to account for  the energy contribution of London dispersion
forces on the total energy of a hydrazine-nickel system.

Remember that DFT-D2 badly overestimate the interaction of molecules with metal surfaces, see Grimme, S.; Antony, J.; Ehrlich, S.; Krieg, H. A
consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. J. Chem. Phys. 2010,
132, 154104. In cases such as N2H2 on Ni I would rather use vdwdf or vdwdf-c09 (see usage and related papers in QE documentation).

------------------------------
&CONTROL
tefield = .TRUE.,
      dipfield = .TRUE.,
      disk_io = 'low',

&SYSTEM
      edir=3,
      emaxpos=0.65,
      eopreg=0.06,
      eamp=0,
------------------------------

This is a well tested but old and complex machine to correct the interaction of a dipole with its periodic replicas along z. I do not know if it is
possible to estimate its impact on dispersion forces in a different way than by using/not using the dipole correction and check the difference between
the above "Dispersion Correction" contribution to the total energy. However, I've satisfactorily used for a system similar to yours (thiol SAM on Au
surface) this new setup (again, read the documentation and related papers), which decouple in a simpler way the dipole along z.

&system
   input_dft='vdw-df-c09'
   assume_isolated = 'esm',
   esm_bc='bc1',
/

HTH
Giuseppe

On Tuesday, May 03, 2016 12:41:49 AM Elliot Menkah wrote:
Hi all,
I'm trying to account for  the energy contribution of London dispersion
forces on the total energy of a hydrazine-nickel system.

Could someone please assist me as to how to account for London
dispersion forces with QE or essentially how to do a DFT-D2 calculation
with the the aim of accounting for the energy contribution of dispersion
forces.

When I correct the net-surface dipole on a system by using the variables
and values below, does it affect the energy from dispersion forces, if
so, how?
How does correcting the net-surface dipole relate to accounting for
dispersion forces?

------------------------------
&CONTROL
tefield = .TRUE.,
      dipfield = .TRUE.,
      disk_io = 'low',

&SYSTEM
      edir=3,
      emaxpos=0.65,
      eopreg=0.06,
      eamp=0,
------------------------------

I'm basically trying to account for London dispersion forces on a
hydrazine-nickel system.
Any info to help my computation would be gladly appreciated.
Thank you

Kind Regards,
Elliot

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  Giuseppe Mattioli
  CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
  v. Salaria Km 29,300 - C.P. 10
  I 00015 - Monterotondo Stazione (RM), Italy
  Tel + 39 06 90672836 - Fax +39 06 90672316
  E-mail: <giuseppe.mattioli at ism.cnr.it<mailto:giuseppe.mattioli at ism.cnr.it>>
  http://www.ism.cnr.it/en/staff/giuseppe-mattioli/
  ResearcherID: F-6308-2012

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