<div dir="ltr"><div class="gmail-gs" style="margin:0px;padding:0px 0px 20px;width:958px;font-family:Roboto,RobotoDraft,Helvetica,Arial,sans-serif;font-size:medium"><div class="gmail-"><div id="gmail-:x7" class="gmail-ii gmail-gt gmail-adO" style="font-size:12.8px;direction:ltr;margin:8px 0px 0px;padding:0px"><div id="gmail-:x6" class="gmail-a3s gmail-aXjCH" style="overflow:hidden;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:small;line-height:1.5;font-family:Arial,Helvetica,sans-serif"><div>Dear All,</div><div><br></div><div dir="ltr">I want to calculate berry phase polarization in KNbO3(KNO).  Ideally, for a perfect cubic KNO the polarization should be zero. However, I’m getting 0.4898671 C/m^2. I’ve no idea why am I getting this result. Can anyone help??<br>below are my <a href="http://scf.in/" target="_blank">scf.in</a>, <a href="http://nscf.in/" target="_blank">nscf.in</a> and polarization part of nscf.out <br><br><div><a href="http://scf.in/" target="_blank">scf.in</a></div><div><br></div>&CONTROL<br>    calculation = 'scf'<br>    restart_mode = 'from_scratch' <br>    outdir = 'c-kno' ,<br>    pseudo_dir = '/berry-phase-kno'<br>    prefix = 'bp-KNO'<br>/<br><br>&SYSTEM<br>    ibrav=1<br>    celldm(1)=7.59934d0<br>    nat=5<br>    ntyp=3<br>    nbnd=40<br>    ecutwfc=70<br>    occupations = 'fixed'<br>    degauss=0.00<br><br>/<br><br>&ELECTRONS<br>    conv_thr    = 1.D-6,<br>    mixing_beta = 0.07<br>/<br><br>ATOMIC_SPECIES<br>    K 39.09830 K.pz-hgh.UPF<br>    Nb 92.90638 Nb.pz-hgh.UPF    <br>    O 15.99940 O.pz-hgh.UPF    <br><br>ATOMIC_POSITIONS {crystal}<br>K        0.000000000   0.000000000   0.000000000<br>Nb      0.500000000   0.500000000   0.500000000<br>O        0.500000000   0.500000000   0.000000000<br>O        0.500000000   0.000000000   0.500000000<br>O        0.000000000   0.500000000   0.500000000<br><br>K_POINTS {automatic} <br>4 4 4  0 0 0<br><br><br><br><br><br><a href="http://nscf.in/" target="_blank">nscf.in</a><br><br>&CONTROL<br>    calculation = 'nscf'<br>    restart_mode = 'from_scratch' <br>    outdir = 'c-kno' <br>    pseudo_dir = '/berry-phase-kno'<br>    prefix = 'bp-KNO'<br>    lberry = .true.<br>    gdir = 3<br>    nppstr = 7<br>/<br><br>&SYSTEM<br>    ibrav=1<br>    celldm(1)=7.59934d0<br>    nat=5<br>    ntyp=3<br>    nbnd=40<br>    ecutwfc=70<br>    occupations = 'fixed'<br>    degauss=0.00<br><br>/<br><br>&ELECTRONS<br>    conv_thr    = 1.D-6<br>    mixing_beta = 0.07<br>/<br><br>ATOMIC_SPECIES<br>    K 39.09830 K.pz-hgh.UPF<br>    Nb 92.90638 Nb.pz-hgh.UPF    <br>    O 15.99940 O.pz-hgh.UPF    <br><br>ATOMIC_POSITIONS {crystal}<br>K        0.000000000   0.000000000   0.000000000<br>Nb      0.500000000   0.500000000   0.500000000<br>O        0.500000000   0.500000000   0.000000000<br>O        0.500000000   0.000000000   0.500000000<br>O        0.000000000   0.500000000   0.500000000<br><br>K_POINTS {automatic} <br>4 4 7  0 0 0<br><br><br><br><br><br><br><br>nscf.out<br><br><br>                             VALUES OF POLARIZATION<br>                             ~~~~~~~~~~~~~~~~~~~~~~<br><br>        The calculation of phases done along the direction of vector 3<br>        of the reciprocal lattice gives the following contribution to<br>        the polarization vector (in different units, and being Omega<br>        the volume of the unit cell):<br><br>           P =   3.8195000  (mod   7.6390000)  (e/Omega).bohr<br><br>           P =   0.0085683  (mod   0.0171367)  e/bohr^2<br><br>           P =   0.4898671  (mod   0.9797342)  C/m^2<br><br>        The polarization direction is:  ( 0.00000 , 0.00000 , 1.00000 )<br><br><br>               ==================================================<div class="gmail-yj6qo gmail-ajU" style="outline:none;padding:10px 0px;width:22px;margin:2px 0px 0px">-- <div id="gmail-:xm" class="gmail-ajR" tabindex="0" style="background-color:rgb(232,234,237);border:none;clear:both;line-height:6px;outline:none;width:24px;border-radius:5.5px"></div></div></div></div></div></div></div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div style="font-size:small"><font face="georgia,serif">Regards,</font></div><div style="font-size:small"><span style="font-family:georgia,serif"><b><i>Rajender Tiwari</i></b></span><font face="georgia,serif"><br></font></div><div style="font-size:small"><span style="font-family:georgia,serif"><br></span></div><div style="font-size:small"><div><span style="color:rgb(0,0,255);font-family:georgia,serif"><i>Ph.D. Scholar</i></span></div><div><span style="color:rgb(0,0,255);font-family:georgia,serif"><i>Special Center for Nano Science</i></span></div><div><i><span style="color:rgb(0,0,255);font-family:georgia,serif">Jawaharlal Nehru University, New Delhi</span><br></i></div><div><i><font color="#0000ff" face="georgia,serif">#+91-</font><span style="color:rgb(0,0,255);font-family:georgia,serif">9868970410/ </span><span style="color:rgb(0,0,255);font-family:georgia,serif">9873513329</span></i></div></div><div style="font-size:small"><img src="https://images.careers360.mobi/sites/default/files/styles/medium/public/2015/03/30/JNU_0.jpg?itok=-Aq8dnbE" alt="Image result for jnu" style="font-size:12.8px" width="96" height="96"></div></div></div></div></div></div></div></div>