<div dir="ltr">Dear Javier,<div><br></div><div>For spin-polarized case, you have <span style="font-size:12.8000001907349px">0.6698526-</span><span style="font-size:12.8000001907349px">1.0038673=-0.3340147,</span></div><div><span style="font-size:12.8000001907349px">value very similar to the spin unpolarized case.</span></div><div><span style="font-size:12.8000001907349px">Polarization is defined only modulo a quantum, and in the above, I just subtracted the quantum.</span></div><div><span style="font-size:12.8000001907349px"><br></span></div><div><span style="font-size:12.8000001907349px">Andrei </span></div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Feb 20, 2015 at 10:27 AM, Nossa, Javier <span dir="ltr"><<a href="mailto:jnossa@carnegiescience.edu" target="_blank">jnossa@carnegiescience.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Dear pwscfers,<br><div>I am calculating the polarization of BaTiO3 and found a different value of it when implementing spin-polarized, nspin=2. </div><div><br></div><div>non-spin-polarized gives P=-0.3340199 (mod 2.0077346) C/m^2, which is correct.</div><div>spin-polarized gives P=0.6698526 (mod 1.0038673) C/m^2, which is not correct.</div><div><br></div><div>Although it seems to be just a factor of two difference in the absolute value of the polarization, it is not exactly a factor of two. It is 2.0054... </div><div>In addition, the sign of the polarization is opposite.</div><div>On the other hand, the mod is exactly a factor of two. </div><div><br></div><div>Why there is such a difference in the polarization?<br></div><div><br></div><div>I am doing this as a test because my real system is magnetic and bigger than BaTiO3.</div><div><br></div><div>Here are the inputs for the nscf calculation:</div><div><br></div><div>spin-polarized:</div><div><div>&control</div><div> calculation='nscf'</div><div> restart_mode='from_scratch',</div><div> prefix='job',</div><div> lberry = .true.</div><div> gdir = 3</div><div> nppstr = 10</div><div> /</div><div>&system</div><div> ibrav= 0, </div><div> celldm(1)=1.0,</div><div> nat= 5, ntyp= 3,</div><div> ecutwfc = 120,</div><div> !occupations='smearing', smearing='gauss', degauss=0.003,</div><div> !occupations='fixed',</div><div> input_dft='wc'</div><div> nspin=2, </div><div> tot_magnetization= 0.0,</div><div>/</div><div>&electrons</div><div>/</div><div>ATOMIC_SPECIES</div><div> Ba 137.327 Ba.wc-n-nc.UPF</div><div> Ti 47.867 Ti.wc-n-nc.UPF </div><div> O 15.9994 O.wc-nc.UPF</div><div>CELL_PARAMETERS (alat=1.0)</div><div> 7.54662 0.0 0.0</div><div> 0.0 7.54662 0.0</div><div> 0.0 0.0 7.74409</div><div>ATOMIC_POSITIONS {crystal}</div><div>Ba 0.00000 0.00000 0.00000</div><div>Ti 0.50000 0.50000 0.48186</div><div>O 0.00000 0.50000 0.51791</div><div>O 0.50000 0.00000 0.51791</div><div>O 0.50000 0.50000 0.03133 </div><div>K_POINTS {automatic}</div><div>4 4 4 0 0 0</div></div><div><br></div><div><br></div><div>non-spin-polarized:</div><div><div>&control</div><div> calculation='nscf'</div><div> restart_mode='from_scratch',</div><div> prefix='job',</div><div> lberry = .true.</div><div> gdir = 3</div><div> nppstr = 10</div><div> /</div><div>&system</div><div> ibrav= 0, </div><div> celldm(1)=1.0,</div><div> nat= 5, ntyp= 3,</div><div> ecutwfc = 120,</div><div> !occupations='smearing', smearing='gauss', degauss=0.003,</div><div> !occupations='fixed',</div><div> input_dft='wc'</div><div>/</div><div>&electrons</div><div>/</div><div>ATOMIC_SPECIES</div><div> Ba 137.327 Ba.wc-n-nc.UPF</div><div> Ti 47.867 Ti.wc-n-nc.UPF </div><div> O 15.9994 O.wc-nc.UPF</div><div>CELL_PARAMETERS (alat=1.0)</div><div> 7.54662 0.0 0.0</div><div> 0.0 7.54662 0.0</div><div> 0.0 0.0 7.74409</div><div>ATOMIC_POSITIONS {crystal}</div><div>Ba 0.00000 0.00000 0.00000</div><div>Ti 0.50000 0.50000 0.48186</div><div>O 0.00000 0.50000 0.51791</div><div>O 0.50000 0.00000 0.51791</div><div>O 0.50000 0.50000 0.03133 </div><div>K_POINTS {automatic}</div><div>4 4 4 0 0 0</div></div><div><br></div><div><br></div><div>Pseudopotentials are taken from THEOS PSLibrary 0.3.1.</div><div><br></div><div>Outputs are attached.</div><div><br></div><div><br></div><div>Thank you very much for your help.</div><span class="HOEnZb"><font color="#888888"><div><br></div><div>-- <br><div><div dir="ltr"><div>With best regards,</div><div>Javier Francisco Nossa<br></div><span style="text-indent:0px;letter-spacing:normal;font-variant:normal;text-align:-webkit-auto;font-style:normal;font-weight:normal;line-height:normal;border-collapse:separate;text-transform:none;font-size:medium;white-space:normal;font-family:Helvetica;word-spacing:0px"><br>Postdoc at Geophysical Laboratory<br>Carnegie Institution of Washington<br>5251 Broad Branch Road, N.W.<br>Washington, DC 20015-1305<br>Tel.: <a value="+12024788906">1.240.476.3993</a><br>E-mail: <a href="mailto:dappleby@ciw.edu" target="_blank">jnossa@carnegiescience.edu</a></span></div></div>
</div></font></span></div>
<br>_______________________________________________<br>
Pw_forum mailing list<br>
<a href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</a><br>
<a href="https://urldefense.proofpoint.com/v2/url?u=http-3A__pwscf.org_mailman_listinfo_pw-5Fforum&d=AwICAg&c=-dg2m7zWuuDZ0MUcV7Sdqw&r=iaCUSkNPjaS0OZmx8CL3zuFJHmomB6kEDsD3Du2Xz38&m=jHc1e4BMDezKEN4w-4Sz3WYY43oEOCVzdofkatuhMr0&s=ptunJ7qbTZCjdsr3TWNH3-Yh3KVY76v7PTd5Aj-blsQ&e=" target="_blank">https://urldefense.proofpoint.com/v2/url?u=http-3A__pwscf.org_mailman_listinfo_pw-5Fforum&d=AwICAg&c=-dg2m7zWuuDZ0MUcV7Sdqw&r=iaCUSkNPjaS0OZmx8CL3zuFJHmomB6kEDsD3Du2Xz38&m=jHc1e4BMDezKEN4w-4Sz3WYY43oEOCVzdofkatuhMr0&s=ptunJ7qbTZCjdsr3TWNH3-Yh3KVY76v7PTd5Aj-blsQ&e=</a> <br></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature"><div dir="ltr">Andrei Malashevich<div>Postdoctoral Associate</div><div>Center for Research on Interface Structures and Phenomena</div><div>Department of Applied Physics</div><div>Yale University</div></div></div>
</div>