[Pw_forum] Monolayer WSe2 band structure related problems

Anindya Bose anindya at iiita.ac.in
Mon Mar 6 12:55:59 CET 2017 

Dear Sir,
I have used this code but I didn't get the direct band gap structure of
monolayer WSe2.
&CONTROL
  calculation='vc-relax',
  outdir='monolayer WSe2',
  prefix='calc',
  pseudo_dir='/home/anindya/Desktop/pseudopotential',
  verbosity='high',
  disk_io='high',
  wf_collect=.true.,
  nstep = 50,
  etot_conv_thr=1d-02,
  forc_conv_thr=1d-02,
/

&SYSTEM
  ibrav=4,
  celldm(1)=6.2020811408d0, celldm(3)=4.3566118221d0,
  nat=3,
  ntyp=2,
  ecutwfc=40.0d0,
  ecutrho =130.0d0,
  nbnd=200,
  vdw_corr='Grimme-D2',
  force_symmorphic=.true.,
  input_dft='PBE',
  occupations='fixed',
/

&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_r.oncvpsp.upf
  W 183.840000d0 W_ONCV_PBE-1.1_r.oncvpsp.upf

ATOMIC_POSITIONS {alat}
  W    0.5000000000d0   0.2886751346d0   2.1782995738d0
  Se   0.5000000000d0  -0.2886751346d0   1.6692977456d0
  Se   0.5000000000d0  -0.2886751346d0   2.6873014019d0

K_POINTS {automatic}
  10 10 1 0 0 0

I have enclosed my output band structure with this mail.Can you please help
me in this regard.How can I get the correct band diagram of monolayer
WSe2(direct bandgap). I have used all the codes for spin calculation and I
got the spin orbit coupling but didn't find perfect band diagram.I will be
waiting for your response.

On Wed, Mar 1, 2017 at 9:04 PM, Giovanni Cantele <
giovanni.cantele at spin.cnr.it> wrote:

> 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> 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> 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.
>> > _______________________________________________
>> > Pw_forum mailing list
>> > Pw_forum at pwscf.org
>> > http://pwscf.org/mailman/listinfo/pw_forum
>>
>> --
>>
>> 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
>>
>>
>>
>> _______________________________________________
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
>> http://pwscf.org/mailman/listinfo/pw_forum
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
>
>
> --
>
> 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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> Pw_forum mailing list
> Pw_forum at pwscf.org
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>
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