[Pw_forum] Monolayer WSe2 band structure related problems

[Giovanni Cantele]

I never use ism, maybe you can read relevant papers in the literature. However, if your purpose is just to simulate an isolated monolayer, just add to the lattice vector orthogonal to the monolayer
plane (a3, in your case) vacuum space, so if the current length is, just to make an example, 5 A, try to use 15 A. This is the so called supercell approach, discussed several times in the forum.

Giovanni

> On 1 Mar 2017, at 16:17, Anindya Bose <anindya at iiita.ac.in> wrote:
> 
> Actually I have used esm_bc to add vacuum in the structure.How can I add vacuum in this monolayer WSE2 structure using quantum espresso.Which code should be used.
> 
> On Wednesday, March 1, 2017, Giovanni Cantele <giovanni.cantele at spin.cnr.it <mailto:giovanni.cantele at spin.cnr.it>> wrote:
> It is not clear how and to what extend your band structure differs from shat you expect.
> However, one issue I can see is that if you want to study MONOLAYER WSe2, you should be aware of the fact that the vacuum space, separating the periodic replicas
> along your z direction should be large enough to prevent them from interacting (otherwise, you are considering a periodic crystal also along
> that direction). Currently, as far as I can see such vacuum is < 5A, definitely too small to simulate a monolayer. Additionally, you also include vdw_corr, usually introduced
> to better describe inter-layer interaction, whereas you are claiming that you want to study a system composed by a single layer.
> Also, I think that you don’t need to use the variable esm_bc just to calculate the properties of a monolayer.
> 
> Giovanni
> 
> 
> 
> 
> > On 1 Mar 2017, at 14:01, Anindya Bose <anindya at iiita.ac.in <javascript:;>> wrote:
> >
> > Dear Sir,
> >
> > &CONTROL
> >   calculation='nscf',
> >   outdir='monolayer WSe2',
> >   prefix='calc',
> >   pseudo_dir='/home/anindya/Desktop/pseudopotentials',
> >   verbosity='low',
> >   disk_io='high',
> >   wf_collect=.true.,
> >   etot_conv_thr=1d-02,
> >   forc_conv_thr=1d-02,
> > /
> >
> > &SYSTEM
> >   noncolin=.true.,
> >   lspinorb=.true.,
> >   ibrav=0,
> >   celldm(1)=6.2020811408d0, celldm(3)=4.3566118221d0,
> >   nat=3,
> >   ntyp=2,
> >   ecutwfc=40.0d0,
> >   nbnd=200,
> >   vdw_corr='Grimme-D2',
> >   starting_magnetization=0.05,
> >   force_symmorphic=.true.,
> >   input_dft='PBE',
> >   esm_bc='bc1',
> >   no_t_rev=.false.,
> > /
> >
> > &ELECTRONS
> >   diagonalization='david',
> >   conv_thr=1d-08,
> >   mixing_mode='plain',
> >   mixing_beta=0.700d0,
> > /
> >
> > &ions
> >   ion_dynamics ='bfgs',
> > /
> >
> > &cell
> >   cell_dynamics ='bfgs',
> >   cell_factor=15,
> > /
> >
> > ATOMIC_SPECIES
> >   Se 78.960000d0 Se_ONCV_PBE-1.0_nr.oncvpsp.upf
> >   W 183.840000d0 W_ONCV_PBE-1.1_nr.oncvpsp.upf
> >
> > CELL_PARAMETERS (alat=  6.20208114)
> >    1.008112278   0.000000000   0.000000000
> >   -0.504056139   0.873050842   0.000000000
> >    0.000000000   0.000000000   2.445357065
> >
> > ATOMIC_POSITIONS {alat}
> >   W        0.504056139   0.291016947   1.222674975
> >   Se       0.504056139  -0.291016947   0.699051439
> >   Se       0.504056139  -0.291016947   1.746298512
> >
> >
> > K_POINTS {crystal_b}
> > 4
> > # Gamma-K-M-Gamma
> > 0 0 0   20 !G
> > 0.33 0.33 0 20 !K
> > 0.5 0 0 20 !M
> > 0 0 0 20 !G
> >
> > I am not getting the WSe2 monolayer band structure, can you please help me in this regard.
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> 
> --
> 
> Giovanni Cantele, PhD
> CNR-SPIN
> c/o Dipartimento di Fisica
> Universita' di Napoli "Federico II"
> Complesso Universitario M. S. Angelo - Ed. 6
> Via Cintia, I-80126, Napoli, Italy
> e-mail: giovanni.cantele at spin.cnr.it <javascript:;>
> Phone: +39 081 676910
> Skype contact: giocan74
> 
> ResearcherID: http://www.researcherid.com/rid/A-1951-2009 <http://www.researcherid.com/rid/A-1951-2009>
> Web page: http://people.na.infn.it/~cantele <http://people.na.infn.it/~cantele>
> 
> 
> 
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-- 

Giovanni Cantele, PhD
CNR-SPIN
c/o Dipartimento di Fisica
Universita' di Napoli "Federico II"
Complesso Universitario M. S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
e-mail: giovanni.cantele at spin.cnr.it
Phone: +39 081 676910
Skype contact: giocan74

ResearcherID: http://www.researcherid.com/rid/A-1951-2009
Web page: http://people.na.infn.it/~cantele

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