<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;">Hi sir,<br><br> Sir i have calculated the band structure of YVO4  and it is coming as near about 0.5 ev .. sir as suggested by you in earlier reply that <br><br>>means band gap at gamma = 0.3058-(-8.9833)=  8.2891<br>>  which is very large ??<br><br>Not necessarily, the offset of band in a periodic system is arbitrary. You  <br>need to know where you Fermi energy is, or which are the HOMO and LUMO of  <br>your system to find the gap.<br><br>I have calculated Fermi energy and it is coming as 6.108. The band gap of YVO4 is 3.9 eV experimental and DFT calculates the band gap as nearly half i.e. it should come as 1.8 eV approx. Please help.. Thanks In advance.My Input files are listed below...<br><br>SCF INPUT<br>===============================================<br><br> &control<br>   
 calculation='scf',<br>    restart_mode='from_scratch',<br>    prefix='yvo'<br>    pseudo_dir = '/home/physics/pseudo/',<br>    outdir='/home/physics/work/yvo/temp'<br> /<br> &system<br>    ibrav =1, a=7.118300514, b= 7.118300514, c=6.289300454<br>, nat =24, ntyp= 3,  ecutwfc = 40.0,ecutrho=300,<br> occupations='smearing', smearing='mp', degauss=0.01, <br><br><br> /<br> &electrons<br>    mixing_beta = 0.7<br>    diagonalization = 'david'<br>    conv_thr =  1.0e-6<br>/<br> &ions<br> /<br><br>ATOMIC_SPECIES<br>  Y     88.90585     Y.pbe-nsp-van.UPF<br>  V     50.9415      V.pbe-sp-van.UPF<br>  O     15.9994     
 O.pbe-van_ak.UPF<br>ATOMIC_POSITIONS {angstrom}<br>Y             0.000000000   5.338725356    0.786162553<br>/<br>/<br><br>K_POINTS {automatic}<br>  4 4 4 0 0 0<br>=======================================================<br>                               Bands Input<br>======================================================<br><br><br> &control<br>    calculation='bands'<br>    pseudo_dir = '/home/physics/pseudo/',<br>    outdir='/home/physics/work/yvo/temp',<br>    prefix='yvo',<br>  <br> /<br> &system<br>    ibrav =1, a=7.118300514, b= 7.118300514, c=6.289300454, nat=24, ntyp=3, <br>ecutwfc = 40.0,ecutrho=300,
 occupations='smearing', smearing='mp', degauss=0.01, nbnd= 115, <br>    <br> /<br> &electrons<br>   mixing_beta=0.7<br>   conv_thr=1.0e-6<br> diagonalization = 'david'<br>/<br>&ions<br> /<br><br>ATOMIC_SPECIES<br> Y       88.90585     Y.pbe-nsp-van.UPF<br>  V      50.9415      V.pbe-sp-van.UPF<br>  O     15.9994      O.pbe-van_ak.UPF<br>ATOMIC_POSITIONS {angstrom}<br>Y             0.000000000   5.338725356    0.786162553<br>\<br>\<br>K_POINTS<br> 26<br>0.000 0.000 0.000  1<br>0.000 0.000 0.125  1<br>0.000 0.000 0.250  1<br>0.000 0.000 0.375  1<br>0.000 0.000 0.500 
 1                             <br>0.125 0.125 0.500  1                             <br>0.250 0.250 0.500  1                             <br>0.375 0.375 0.500  1                            <br>0.500 0.500 0.500  1                             <br>0.500
 0.500 0.333  1                             <br>0.500 0.500 0.166  1                             <br>0.500 0.500 0.000  1                             <br>0.375 0.375 0.000  1                             <br>0.250 0.250 0.000 
 1                             <br>0.125 0.125 0.000  1                             <br>0.000 0.000 0.000  1                             <br>0.000 0.000 0.166  1                            <br>0.000 0.000 0.333  1                             <br>0.000
 0.166 0.500  1                           <br>0.000 0.333 0.500  1                            <br>0.000 0.500 0.500  1                             <br>0.000 0.500 0.333  1                             <br>0.000 0.500 0.166  1                            
 <br>0.000 0.500 0.000  1                             <br>0.000 0.333 0.000  1                             <br>0.000 0.166 0.000  1 <br>============================================================<br>===========================================================<br> &inputpp<br>    prefix  = 'yvo'<br>    outdir = '/home/physics/work/yvo/temp'<br>    filband = 'yvobands.dat'<br>/<br>========================================<br>Plotband INPUTS<br>=======================================<br>yvobands.dat<br>-10  12<br>yvobands.xmgr<br>yvobands.ps<br>6.1088<br>1.0 
 0.00<br>================================================<br>============================================<br><br>With regards,<br>Neel Singh<br>Univeristy of Delhi<br>--- On <b>Tue, 28/7/09, Lorenzo Paulatto <i><paulatto@sissa.it></i></b> wrote:<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;"><br>From: Lorenzo Paulatto <paulatto@sissa.it><br>Subject: Re: [Pw_forum] Not getting right Band structure<br>To: "PWSCF Forum" <pw_forum@pwscf.org><br>Date: Tuesday, 28 July, 2009, 10:07 AM<br><br><div class="plainMail">In data 28 luglio 2009 alle ore 11:54:14, Neel Singh  <br><<a ymailto="mailto:neelphysics@yahoo.in" href="/mc/compose?to=neelphysics@yahoo.in">neelphysics@yahoo.in</a>> ha scritto:<br>> means band gap at gamma = 0.3058-(-8.9833)=  8.2891<br>>  which is very large ??<br><br>Not necessarily, the offset of band in a periodic system is arbitrary. You 
 <br>need to know where you Fermi energy is, or which are the HOMO and LUMO of  <br>your system to find the gap.<br><br><br>> 2) In the output of SCF and Bands , the output file has 4 warnings<br><br>This a very frequently asked question, please see the corresponing entry  <br>in the manual:<br><a href="http://www.pwscf.org/guide/2.1.2/html-node/node56.html" target="_blank">http://www.pwscf.org/guide/2.1.2/html-node/node56.html</a><br><a href="http://www.pwscf.org/guide/2.1.2/html-node/node57.html" target="_blank">http://www.pwscf.org/guide/2.1.2/html-node/node57.html</a><br><br><br>> for this I have already increase the following quantities  in the   <br>> increments<br>> kinetic-energy cutoff     =      40.0000  Ry to 60<br>>      charge density cutoff     =     250.0000  Ry to 400<br>> But still the
 warnings are there.<br><br>It is not a big increment of the cutoff that will solve this problem, but  <br>a small increment or nr1, nr2 nr3<br><br>cheers, and good work<br><br>-- <br>Lorenzo Paulatto<br>SISSA  &  DEMOCRITOS (Trieste)<br>phone: +39 040 3787 511<br>skype: paulatz<br>www:   <a href="http://people.sissa.it/%7Epaulatto/" target="_blank">http://people.sissa.it/~paulatto/</a><br><br>     *** save italian brains ***<br>  <a href="http://saveitalianbrains.wordpress.com/" target="_blank">http://saveitalianbrains.wordpress.com/</a><br>_______________________________________________<br>Pw_forum mailing list<br><a ymailto="mailto:Pw_forum@pwscf.org" href="/mc/compose?to=Pw_forum@pwscf.org">Pw_forum@pwscf.org</a><br><a href="http://www.democritos.it/mailman/listinfo/pw_forum" target="_blank">http://www.democritos.it/mailman/listinfo/pw_forum</a><br></div></blockquote></td></tr></table><br>
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