[Pw_forum] Monolayer WSe2 band structure related problems

[Ari P Seitsonen]

Dear Anindya,

   Please provide your affiliation - to respect the other subscribers of 
the forum (please go through the instructions on how to post to the 
forum).

   Adding to the other items mentioned in the previous responses, I would 
like to point out that apparently you want to relax the lateral lattice 
constant of the cell, but without further options also the vertical 
lattice constant is optimised, and probably the vacuum is either reducing 
or increasing (it never goes to zero, due to numerical precision if 
nothing else; also the DFT+D2 dispersion correction has a long tail): 
Please check the input option 'cell_dofree'.

   'cell_factor = 15' does not make much sense; your threhould variables 
'etot_conv_thr' and 'forc_conv_thr' look very loose to me. Are you sure 
about "disk_io = 'high'"?

     Greetings,

        apsi

-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
   Ari Paavo Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
     Ecole Normale Supérieure (ENS), Département de Chimie, Paris
     Mobile (F) : +33 789 37 24 25    (CH) : +41 79 71 90 935


On Mon, 6 Mar 2017, Anindya Bose wrote:

> 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.
>