[Pw_forum] Monolayer WSe2 band structure related problems

[Giovanni Cantele]

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.
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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