[Pw_forum] Query regarding vdW Griemme Correction

[Giuseppe Mattioli]

Dear Shashi Bhusan Mishra

Please read carefully the input manual:

    Variable:       vdw_corr

    Type:           CHARACTER
    Default:        'none'
    See:            london_s6, london_rcut, london_c6, london_rvdw,  
ts_vdw_econv_thr, ts_vdw_isolated, xdm_a1, xdm_a2
    Description:
                    Type of Van der Waals correction. Allowed values:

                    'grimme-d2', 'Grimme-D2', 'DFT-D', 'dft-d'  :
                         Semiempirical Grimme's DFT-D2.
                         Optional variables: "london_s6",  
"london_rcut", "london_c6", "london_rvdw",
                         S. Grimme, J. Comp. Chem. 27, 1787 (2006),  
doi:10.1002/jcc.20495
                         V. Barone et al., J. Comp. Chem. 30, 934  
(2009), doi:10.1002/jcc.21112

                    'TS', 'ts', 'ts-vdw', 'ts-vdW', 'tkatchenko-scheffler' :
                         Tkatchenko-Scheffler dispersion corrections  
with first-principle derived
                         C6 coefficients (implemented in CP only).
                         Optional variables: "ts_vdw_econv_thr",  
"ts_vdw_isolated"
                         See A. Tkatchenko and M. Scheffler, PRL 102,  
073005 (2009).

                    'XDM', 'xdm' :
                         Exchange-hole dipole-moment model. Optional  
variables: "xdm_a1", "xdm_a2"
                         A. D. Becke et al., J. Chem. Phys. 127,  
154108 (2007), doi:10.1063/1.2795701
                         A. Otero de la Roza et al., J. Chem. Phys.  
136, 174109 (2012),
                         doi:10.1063/1.4705760

                    Note that non-local functionals (eg vdw-DF) are  
NOT specified here but in "input_dft"

Therefore, if you want to use the sempiempirical Grimme's DFT-D2  
correction you should *only* put

vdw_corr='grimme-d2'

in your input file. vdw-df refers to a *different* family of non-local  
ab initio functionals for the calculation of dispersion forces. Its  
use is *alternative* to the use of DFT-D2-

HTH
Giuseppe

Quoting shashi bhusan mishra <mshashi125 at gmail.com>:

> Dear Users,
>            I have a confusion about adding van der waal's grimme correction
> to my system. In my system I have put a adsorbate layer on top of a
> substrate, the distance of separation is around 4 angstrom but when I add
> vdw correction the separation decreases to 3.2 angstrom. With inclusion of
> only vdW interaction, I got the separation and the adsorption energy.
> However, I need to add Grimme D2 type vdW correction. Do I need to write
>
> ​
> input_dft='vdw-DF'
>                           vdw_corr = 'Grimme-D2'​
>
> or    only the correction: vdw_corr= 'Grimme-D2' without mention input dft.
> I am attaching the input file. Please, let me know correction inclusion of
> grimme vdW correction. This varition leads to differnt separation as well
> as adsorption energy.
>
>
> Thanks and regards,
>
> Shashi Bhusan Mi
> ​shra​
>
> Research Scholar,
> ​
> ​
> Dept.
> ​o​
> f Physics,
> IIT Madras-36
>
>
>
>
> ​​


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    Giuseppe Mattioli
    CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
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    I 00015 - Monterotondo Stazione (RM)
    Tel + 39 06 90672836 - Fax +39 06 90672316
    E-mail: <giuseppe.mattioli at ism.cnr.it>
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    ResearcherID: F-6308-2012