[Pw_forum] Implementation of Van der Waals Interactions

[Manuel Otero]

Dear Giuseppe.

Thank you for  your answer.

I tried to use diferent  input_dft. But the calculation does not work.
I have this type of error:
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
     from read_kernel_table : error #         1
     No \"vdW_kernel_table\" file could be found
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

I read that the psedopotencial already have a selected input_dft and I cant
change it.
I restart my calculation using the PBE pseudopotencial and london_s6=0.75
to see if I have better results.
If this does not work I will try to use de svn version.

Thanks again.

Manuel


2013/11/20 Giuseppe Mattioli <giuseppe.mattioli at ism.cnr.it>

>
> Dear Manuel
> Quantum ESPRESSO uses several approaches to simulate, in an ab initio as
> well as in a semiempirical fashion, the dispersion interactions. However,
> the
> information on this subject is still far from being well organized...:-)
>
> As you already know, the semiempirical DFT-D2 approach is invoked by the
> following keywords, which I copy from the PW manual
>
>    +--------------------------------------------------------------------
>    Variable:       london
>
>    Type:           LOGICAL
>    Default:        .FALSE.
>    Description:    if .TRUE. compute semi-empirical dispersion term
> (DFT-D).
>                    See S. Grimme, J. Comp. Chem. 27, 1787 (2006), and
>                    V. Barone et al., J. Comp. Chem. 30, 934 (2009).
>    +--------------------------------------------------------------------
>
>    +--------------------------------------------------------------------
>    Variable:       london_s6
>
>    Type:           REAL
>    Default:        0.75
>    Description:    global scaling parameter for DFT-D. Default is good for
> PBE.
>    +--------------------------------------------------------------------
>
>    +--------------------------------------------------------------------
>    Variable:       london_rcut
>
>    Type:           REAL
>    Default:        200
>    Description:    cutoff radius (a.u.) for dispersion interactions
>
> As you see, the london_s6=0.75 default is considered good for PBE. Without
> further information about your input file this seems to be the only source
> of discrepancy between Persson's results and yours.
>
> Regarding the (more or less) ab initio approaches, the stable 5.0.2
> version (but also 4.3.2, if I remember well) contains the long-range VDW-DF
> correlation functional in different flavours. They are invoked by the
> keyword
>
> input_dft='XXXX'
>
> A complete list of functionals can be found in this file:
>
> YOURQE/Modules/funct.f90
>
> from where the following values of the input_dft variable are extracted
>
>   !              "vdw-df"= "sla+pw+rpb+vdw1"   = vdW-DF
>   !              "vdw-df2"="sla+pw+rw86+vdw2"  = vdW-DF2
>   !              "vdw-df-c09"="sla+pw+c09x+vdw1"
>   !              "vdw-df2-c09"="sla+pw+c09x+vdw2"
>
> Flick through the corresponding documentation to check which kind of
> pseudopotential is required/suggested for the above functionals.
> More choice is allowed in the unstable (but completely working...) svn
> version. The Thatchenko-Scheffler method is now implemented among the cp.x
> options, while the XDM method (for PAW pseudopotentials only) is a new
> feature of pw.x.
>
> HTH
>
> Giuseppe
>
>
> On Tuesday 19 November 2013 20:44:38 Manuel Otero wrote:
> > I am a new user of Quantum-Espresso (QE) and I am trying to study the
> > adsorption energy of lithium ions in graphite. I want to reproduce some
> > calculations from other people (Persson), to ensure that I am using the
> > right parameters.
> >
> > In this system the Van der Waals (vdw) interactions play an important
> role
> > and I want to know more about vdw in QE.
> > In her work Persson (Nano Lett., 2012, 12 (9), pp 4624–4628) says that
> > there are two approacches to include vdw interactions:
> > - "DFT-D2 approach, which adds a semiempirical pairwise force field"
> > - "vdW-DF approach, which adds a nonlocal correlation functional that
> > approximately account for dispersion interactions"
> > which approach use by QE?
> >
> > I am using espresso-4.3.2. In my calculations I use:
> >
> > &SYSTEM
> > ...
> >   london = .true.,
> >   london_rcut =200,
> >   london_s6 =0.75,
> >
> > and
> >
> > ATOMIC_SPECIES
> >  C  12.0107    C.pw91-van_ak.UPF
> > Li   6.939    Li.pw91-n-van.UPF
> >
> > I cant reproduce Persson calculations, but I dont know where is the
> > problem.
> >
> > It is OK to use this parametres with this pseudopotentials?
> > I have tryed changing the parametres but my calculations do not improve.
> >
> > QE enables to change other parameters?
> >
> > Thanks in advance for any help.
> >
> > Manuel
>
>
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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)
>    Tel + 39 06 90672836 - Fax +39 06 90672316
>    E-mail: <giuseppe.mattioli at ism.cnr.it>
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