[Pw_forum] vdw correction for Bi-layer grahene

[plgong]

Dear Paolo Giannozzi, 
   Thanks for your reply and useful files. I have used 'vdw-df' to correct to PBE functional in bilayer graphene, and get
good results (3.40 angstrom). Some tips should be noted. One should not provide a primitive structure with large deviation
from equilibrium, e.g, 5.0 angstorm for layer-distance is bad guess. On the other hand, I think of 'vdw-df' as a correction
for LDA meaningless although it gives somelike results. Because this kind of correction is added for GGA. 
  So, I want to konw whether my second opition is right? BTW, I also donnot understand why you set 'input_dft='Pz' but with
PBE fubction. 

Best wishes

P. L. Gong


> -----原始邮件-----
> 发件人: "Paolo Giannozzi" <paolo.giannozzi at uniud.it>
> 发送时间: 2014年10月17日 星期五
> 收件人: "PWSCF Forum" <pw_forum at pwscf.org>
> 抄送: 
> 主题: Re: [Pw_forum] vdw correction for Bi-layer grahene
> 
> Please see some slides and an example (graphite) here:
>   http://www.fisica.uniud.it/~giannozz/Public/vdw.tar.gz
> P.
> 
> On Fri, 2014-10-17 at 18:56 +0800, plgong wrote:
> > Dear pwscf user,
> >    Recently, I calculated Bilayer graphene with vdw correction. In version of 4.3, the parameter of London can be set to 'true'
> > and then add vdw correction to Exc. In version of 5.1, more options can do it, such as, 'grimmer-d2', 'dft-d'. However, many tests have been performed but I cannot get the layer-distance (3.34 angstrom in experiment). I uesd GGA-PBE and LDA-PZ with vdw, recepetively. The final results shows small distance (3.0 angstrom). I donnot know why leads to the small distance.  So, I still tested the Ecut (30Ry-60Ry0) and vaccum (10-20 angstrom), but the problem was the same. 
> > The input file is,
> > 
> > &CONTROL
> >                  calculation = 'relax' ,
> >                       outdir ='./tmp' ,
> >                 restart_mode = 'from_scratch' ,
> >                   pseudo_dir ='/home/plgong/pseudo',
> >                etot_conv_thr = 1.0e-4 ,
> >                forc_conv_thr = 1.0e-3 ,
> >                     prefix='graphene',
> >  /
> >  &SYSTEM
> >                        ibrav = 4,
> >                            a =2.46
> >                            c =10.0
> >                          nat = 4,
> >                         ntyp = 1,
> >                      ecutwfc = 30.D0 ,
> >                      ecutrho = 240.0 ,
> >                   vdw_corr='grimme-d2'
> >                  tot_charge = 0.00,
> >                  occupations = 'smearing' ,
> >                      degauss = 0.02 ,
> >                                          smearing='mv'
> > 
> >  /
> >  &ELECTRONS
> >                     conv_thr = 1.D-7 ,
> >                      mixing_beta=0.3
> >                      mixing_mode='local-TF'
> >                 electron_maxstep=300
> >  /
> >  &IONS
> >                 ion_dynamics = 'bfgs' ,
> > 
> >  /
> > ATOMIC_SPECIES
> >    C    12.00000   C.pz-rrkjus.UPF
> > ATOMIC_POSITIONS {crystal}
> > C  0.000000  0.000000  0.500000
> > C  0.333333  0.666667  0.500000
> > C  0.000000  0.000000  0.834000
> > C  0.666667  0.333333  0.834000
> > K_POINTS {automatic}
> > 30 30 1   0 0 0
> > 
> > Can anyone help me to solve it? 
> > 
> > P. L. Gong
> > ISSP CAS, HeFei, China
> > 
> > 
> > 
> > --
> > 
> > ====================================================
> > Addr: Institute of Solid State Physics, Chinese Academy of 
> > Sciences, Hefei, Anhui 230031, China
> > Tel: +86-551-65591591(office), 18756086113(cell phone)
> > Email: plgong at theory.issp.ac.cn
> > ========================================================================
> > 
> > 
> > 
> > 
> > 
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> 
> -- 
>  Paolo Giannozzi, Dept. Chemistry&Physics&Environment, 
>  Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
>  Phone +39-0432-558216, fax +39-0432-558222 
> 
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--

====================================================
Addr: Institute of Solid State Physics, Chinese Academy of 
Sciences, Hefei, Anhui 230031, China
Tel: +86-551-65591591(office), 18756086113(cell phone)
Email: plgong at theory.issp.ac.cn
========================================================================