[Pw_forum] Implementation of Van der Waals Interactions
Ari P Seitsonen
Ari.P.Seitsonen at iki.fi
Mon Nov 25 04:24:14 CET 2013
Dear Manuel,
If indeed using the version, please have a look at
<QE-root>/bin/generate_vdW_kernel_table.x
generated from
PW/generate_vdW_kernel_table.f90
You have to run this program once first. It will generate you the kernel
table needed. In the present versions this table resides in the same place
as the pseudo potentials, I don't remember about the version 4.3.2.
Hopefully this helps.
Greetings from Zurich,
apsi
-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
Ari P Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
Physikalisch-Chemisches Institut der Universitaet Zuerich
Tel: +41 44 63 54 497 / Mobile: +41 79 71 90 935
On Sun, 24 Nov 2013, Manuel Otero wrote:
> 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
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> E-mail: <giuseppe.mattioli at ism.cnr.it>
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