<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">BEFORE trying vc-relax (what is the structure corresponding to the band structure you give in input?), try calculation=relax and<div class="">calculate band structure.</div><div class=""><br class=""></div><div class="">Why do you need nbnd=200?</div><div class=""><br class=""></div><div class="">For SURE ecutrho is WRONG. </div><div class="">For norm-conserving pseudo potentials (as yours), ecutrho = 4 * ecutwfc (a smaller value will definitely produce WRONG results,</div><div class="">to what extent is maybe unpredictable), otherwise ecutrho is usually 6 to 12 times ecutwfc.</div><div class=""><br class=""></div><div class="">Are you sure about your pseudos?</div><div class=""><br class=""></div><div class="">Finally: how do you set the “zero energy”?</div><div class=""><br class=""></div><div class="">Giovanni</div><div class=""><br class=""></div><div class=""><br class=""><div><blockquote type="cite" class=""><div class="">On 6 Mar 2017, at 12:55, Anindya Bose <<a href="mailto:anindya@iiita.ac.in" class="">anindya@iiita.ac.in</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class=""><div class=""><div class="">Dear Sir,<br class=""></div>I have used this code but I didn't get the direct band gap structure of monolayer WSe2.<br class="">&CONTROL<br class=""> calculation='vc-relax',<br class=""> outdir='monolayer WSe2',<br class=""> prefix='calc',<br class=""> pseudo_dir='/home/anindya/Desktop/pseudopotential',<br class=""> verbosity='high',<br class=""> disk_io='high',<br class=""> wf_collect=.true.,<br class=""> nstep = 50,<br class=""> etot_conv_thr=1d-02,<br class=""> forc_conv_thr=1d-02,<br class="">/<br class=""><br class="">&SYSTEM<br class=""> ibrav=4,<br class=""> celldm(1)=6.2020811408d0, celldm(3)=4.3566118221d0,<br class=""> nat=3,<br class=""> ntyp=2,<br class=""> ecutwfc=40.0d0,<br class=""> ecutrho =130.0d0,<br class=""> nbnd=200,<br class=""> vdw_corr='Grimme-D2',<br class=""> force_symmorphic=.true.,<br class=""> input_dft='PBE',<br class=""> occupations='fixed',<br class="">/<br class=""><br class="">&ELECTRONS<br class=""> diagonalization='david',<br class=""> conv_thr=1d-08,<br class=""> mixing_mode='plain',<br class=""> mixing_beta=0.700d0,<br class="">/<br class=""><br class="">&ions<br class=""> ion_dynamics ='bfgs',<br class="">/<br class=""> <br class="">&cell<br class=""> cell_dynamics ='bfgs',<br class=""> cell_factor=15,<br class="">/<br class=""><br class="">ATOMIC_SPECIES<br class=""> Se 78.960000d0 Se_ONCV_PBE-1.0_r.oncvpsp.upf<br class=""> W 183.840000d0 W_ONCV_PBE-1.1_r.oncvpsp.upf<br class=""><br class="">ATOMIC_POSITIONS {alat}<br class=""> W 0.5000000000d0 0.2886751346d0 2.1782995738d0<br class=""> Se 0.5000000000d0 -0.2886751346d0 1.6692977456d0<br class=""> Se 0.5000000000d0 -0.2886751346d0 2.6873014019d0<br class=""><br class="">K_POINTS {automatic}<br class=""> 10 10 1 0 0 0<br class=""><br class=""></div>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.</div><div class="gmail_extra"><br class=""><div class="gmail_quote">On Wed, Mar 1, 2017 at 9:04 PM, Giovanni Cantele <span dir="ltr" class=""><<a href="mailto:giovanni.cantele@spin.cnr.it" target="_blank" class="">giovanni.cantele@spin.cnr.it</a>></span> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word" class="">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<div class="">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.</div><span class="HOEnZb"><font color="#888888" class=""><div class=""><br class=""></div><div class="">Giovanni</div></font></span><div class=""><div class="h5"><div class=""><br class=""><div class=""><blockquote type="cite" class=""><div class="">On 1 Mar 2017, at 16:17, Anindya Bose <<a href="mailto:anindya@iiita.ac.in" target="_blank" class="">anindya@iiita.ac.in</a>> wrote:</div><br class="m_-4350864146537980139Apple-interchange-newline"><div class="">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.<br class=""><br class="">On Wednesday, March 1, 2017, Giovanni Cantele <<a href="mailto:giovanni.cantele@spin.cnr.it" target="_blank" class="">giovanni.cantele@spin.cnr.it</a>> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">It is not clear how and to what extend your band structure differs from shat you expect.<br class="">
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<br class="">
along your z direction should be large enough to prevent them from interacting (otherwise, you are considering a periodic crystal also along<br class="">
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<br class="">
to better describe inter-layer interaction, whereas you are claiming that you want to study a system composed by a single layer.<br class="">
Also, I think that you don’t need to use the variable esm_bc just to calculate the properties of a monolayer.<br class="">
<br class="">
Giovanni<br class="">
<br class="">
<br class="">
<br class="">
<br class="">
> On 1 Mar 2017, at 14:01, Anindya Bose <<a class="">anindya@iiita.ac.in</a>> wrote:<br class="">
><br class="">
> Dear Sir,<br class="">
><br class="">
> &CONTROL<br class="">
> calculation='nscf',<br class="">
> outdir='monolayer WSe2',<br class="">
> prefix='calc',<br class="">
> pseudo_dir='/home/anindya/Des<wbr class="">ktop/pseudopotentials',<br class="">
> verbosity='low',<br class="">
> disk_io='high',<br class="">
> wf_collect=.true.,<br class="">
> etot_conv_thr=1d-02,<br class="">
> forc_conv_thr=1d-02,<br class="">
> /<br class="">
><br class="">
> &SYSTEM<br class="">
> noncolin=.true.,<br class="">
> lspinorb=.true.,<br class="">
> ibrav=0,<br class="">
> celldm(1)=6.2020811408d0, celldm(3)=4.3566118221d0,<br class="">
> nat=3,<br class="">
> ntyp=2,<br class="">
> ecutwfc=40.0d0,<br class="">
> nbnd=200,<br class="">
> vdw_corr='Grimme-D2',<br class="">
> starting_magnetization=0.05,<br class="">
> force_symmorphic=.true.,<br class="">
> input_dft='PBE',<br class="">
> esm_bc='bc1',<br class="">
> no_t_rev=.false.,<br class="">
> /<br class="">
><br class="">
> &ELECTRONS<br class="">
> diagonalization='david',<br class="">
> conv_thr=1d-08,<br class="">
> mixing_mode='plain',<br class="">
> mixing_beta=0.700d0,<br class="">
> /<br class="">
><br class="">
> &ions<br class="">
> ion_dynamics ='bfgs',<br class="">
> /<br class="">
><br class="">
> &cell<br class="">
> cell_dynamics ='bfgs',<br class="">
> cell_factor=15,<br class="">
> /<br class="">
><br class="">
> ATOMIC_SPECIES<br class="">
> Se 78.960000d0 Se_ONCV_PBE-1.0_nr.oncvpsp.upf<br class="">
> W 183.840000d0 W_ONCV_PBE-1.1_nr.oncvpsp.upf<br class="">
><br class="">
> CELL_PARAMETERS (alat= 6.20208114)<br class="">
> 1.008112278 0.000000000 0.000000000<br class="">
> -0.504056139 0.873050842 0.000000000<br class="">
> 0.000000000 0.000000000 2.445357065<br class="">
><br class="">
> ATOMIC_POSITIONS {alat}<br class="">
> W 0.504056139 0.291016947 1.222674975<br class="">
> Se 0.504056139 -0.291016947 0.699051439<br class="">
> Se 0.504056139 -0.291016947 1.746298512<br class="">
><br class="">
><br class="">
> K_POINTS {crystal_b}<br class="">
> 4<br class="">
> # Gamma-K-M-Gamma<br class="">
> 0 0 0 20 !G<br class="">
> 0.33 0.33 0 20 !K<br class="">
> 0.5 0 0 20 !M<br class="">
> 0 0 0 20 !G<br class="">
><br class="">
> I am not getting the WSe2 monolayer band structure, can you please help me in this regard.<br class="">
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--<br class="">
<br class="">
Giovanni Cantele, PhD<br class="">
CNR-SPIN<br class="">
c/o Dipartimento di Fisica<br class="">
Universita' di Napoli "Federico II"<br class="">
Complesso Universitario M. S. Angelo - Ed. 6<br class="">
Via Cintia, I-80126, Napoli, Italy<br class="">
e-mail: <a class="">giovanni.cantele@spin.cnr.it</a><br class="">
Phone: +39 081 676910<br class="">
Skype contact: giocan74<br class="">
<br class="">
ResearcherID: <a href="http://www.researcherid.com/rid/A-1951-2009" target="_blank" class="">http://www.researcherid.com/ri<wbr class="">d/A-1951-2009</a><br class="">
Web page: <a href="http://people.na.infn.it/~cantele" target="_blank" class="">http://people.na.infn.it/~cant<wbr class="">ele</a><br class="">
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-- <br class=""><br class="">Giovanni Cantele, PhD<br class="">CNR-SPIN<br class="">c/o Dipartimento di Fisica<br class="">Universita' di Napoli "Federico II"<br class="">Complesso Universitario M. S. Angelo - Ed. 6<br class="">Via Cintia, I-80126, Napoli, Italy<br class="">e-mail: <a href="mailto:giovanni.cantele@spin.cnr.it" target="_blank" class="">giovanni.cantele@spin.cnr.it</a><br class="">Phone: +39 081 676910<br class="">Skype contact: giocan74<br class=""><br class="">ResearcherID: <a href="http://www.researcherid.com/rid/A-1951-2009" target="_blank" class="">http://www.researcherid.com/<wbr class="">rid/A-1951-2009</a><br class="">Web page: <a href="http://people.na.infn.it/~cantele" target="_blank" class="">http://people.na.infn.it/~<wbr class="">cantele</a><br class="">
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-- <br class=""><br class="">Giovanni Cantele, PhD<br class="">CNR-SPIN<br class="">c/o Dipartimento di Fisica<br class="">Universita' di Napoli "Federico II"<br class="">Complesso Universitario M. S. Angelo - Ed. 6<br class="">Via Cintia, I-80126, Napoli, Italy<br class="">e-mail: <a href="mailto:giovanni.cantele@spin.cnr.it" class="">giovanni.cantele@spin.cnr.it</a><br class="">Phone: +39 081 676910<br class="">Skype contact: giocan74<br class=""><br class="">ResearcherID: <a href="http://www.researcherid.com/rid/A-1951-2009" class="">http://www.researcherid.com/rid/A-1951-2009</a><br class="">Web page: <a href="http://people.na.infn.it/~cantele" class="">http://people.na.infn.it/~cantele</a><br class="">
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