<div dir="ltr">Dear Giuseppe.<br><br>Thank you for your answer.<br><br>I tried to use diferent input_dft. But the calculation does not work.<br>I have this type of error:<br> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%<br>
from read_kernel_table : error # 1<br> No \"vdW_kernel_table\" file could be found<br> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%<br><br>I read that the psedopotencial already have a selected input_dft and I cant change it.<br>
I restart my calculation using the PBE pseudopotencial and london_s6=0.75 to see if I have better results.<br>If this does not work I will try to use de svn version.<br><br>Thanks again.<br><br>Manuel</div><div class="gmail_extra">
<br><br><div class="gmail_quote">2013/11/20 Giuseppe Mattioli <span dir="ltr"><<a href="mailto:giuseppe.mattioli@ism.cnr.it" target="_blank">giuseppe.mattioli@ism.cnr.it</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
Dear Manuel<br>
Quantum ESPRESSO uses several approaches to simulate, in an ab initio as well as in a semiempirical fashion, the dispersion interactions. However, the<br>
information on this subject is still far from being well organized...:-)<br>
<br>
As you already know, the semiempirical DFT-D2 approach is invoked by the following keywords, which I copy from the PW manual<br>
<br>
+--------------------------------------------------------------------<br>
Variable: london<br>
<br>
Type: LOGICAL<br>
Default: .FALSE.<br>
Description: if .TRUE. compute semi-empirical dispersion term (DFT-D).<br>
See S. Grimme, J. Comp. Chem. 27, 1787 (2006), and<br>
V. Barone et al., J. Comp. Chem. 30, 934 (2009).<br>
+--------------------------------------------------------------------<br>
<br>
+--------------------------------------------------------------------<br>
Variable: london_s6<br>
<br>
Type: REAL<br>
Default: 0.75<br>
Description: global scaling parameter for DFT-D. Default is good for PBE.<br>
+--------------------------------------------------------------------<br>
<br>
+--------------------------------------------------------------------<br>
Variable: london_rcut<br>
<br>
Type: REAL<br>
Default: 200<br>
Description: cutoff radius (a.u.) for dispersion interactions<br>
<br>
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<br>
of discrepancy between Persson's results and yours.<br>
<br>
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<br>
correlation functional in different flavours. They are invoked by the keyword<br>
<br>
input_dft='XXXX'<br>
<br>
A complete list of functionals can be found in this file:<br>
<br>
YOURQE/Modules/funct.f90<br>
<br>
from where the following values of the input_dft variable are extracted<br>
<br>
! "vdw-df"= "sla+pw+rpb+vdw1" = vdW-DF<br>
! "vdw-df2"="sla+pw+rw86+vdw2" = vdW-DF2<br>
! "vdw-df-c09"="sla+pw+c09x+vdw1"<br>
! "vdw-df2-c09"="sla+pw+c09x+vdw2"<br>
<br>
Flick through the corresponding documentation to check which kind of pseudopotential is required/suggested for the above functionals.<br>
More choice is allowed in the unstable (but completely working...) svn version. The Thatchenko-Scheffler method is now implemented among the cp.x<br>
options, while the XDM method (for PAW pseudopotentials only) is a new feature of pw.x.<br>
<br>
HTH<br>
<br>
Giuseppe<br>
<div><div class="h5"><br>
<br>
On Tuesday 19 November 2013 20:44:38 Manuel Otero wrote:<br>
> I am a new user of Quantum-Espresso (QE) and I am trying to study the<br>
> adsorption energy of lithium ions in graphite. I want to reproduce some<br>
> calculations from other people (Persson), to ensure that I am using the<br>
> right parameters.<br>
><br>
> In this system the Van der Waals (vdw) interactions play an important role<br>
> and I want to know more about vdw in QE.<br>
> In her work Persson (Nano Lett., 2012, 12 (9), pp 4624–4628) says that<br>
> there are two approacches to include vdw interactions:<br>
> - "DFT-D2 approach, which adds a semiempirical pairwise force field"<br>
> - "vdW-DF approach, which adds a nonlocal correlation functional that<br>
> approximately account for dispersion interactions"<br>
> which approach use by QE?<br>
><br>
> I am using espresso-4.3.2. In my calculations I use:<br>
><br>
> &SYSTEM<br>
> ...<br>
> london = .true.,<br>
> london_rcut =200,<br>
> london_s6 =0.75,<br>
><br>
> and<br>
><br>
> ATOMIC_SPECIES<br>
> C 12.0107 C.pw91-van_ak.UPF<br>
> Li 6.939 Li.pw91-n-van.UPF<br>
><br>
> I cant reproduce Persson calculations, but I dont know where is the<br>
> problem.<br>
><br>
> It is OK to use this parametres with this pseudopotentials?<br>
> I have tryed changing the parametres but my calculations do not improve.<br>
><br>
> QE enables to change other parameters?<br>
><br>
> Thanks in advance for any help.<br>
><br>
> Manuel<br>
<br>
<br>
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