<div dir="ltr"><div>Dear Giovanni Cantele,<br><br></div>Thank you so much for the detailed response. As my last question, what is the exact difference between starting magnetization and total magnetization?<br></div><div class="gmail_extra"><br clear="all"><div><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div><span style="color:rgb(0,0,0)"><span style="background-color:rgb(255,255,255)"><b>--</b></span></span></div><div><span style="color:rgb(0,0,0)"><span style="background-color:rgb(255,255,255)"><i style="font-size:12.8px">Regards,</i></span></span></div><div><span style="color:rgb(0,0,0)"><span style="background-color:rgb(255,255,255)"><i>Ashkan Shekaari</i></span></span></div><div><span style="color:rgb(0,0,0)"><span style="background-color:rgb(255,255,255)"><i>Plasma Physics Research Center</i></span></span></div><div><span style="color:rgb(0,0,0)"><span style="background-color:rgb(255,255,255)"><i style="font-size:12.8px"><span style="font-size:12.8px">Science and Research Branch</span></i></span></span></div><div><span style="color:rgb(0,0,0)"><span style="background-color:rgb(255,255,255)"><i>I A U, <span style="font-size:12.8px">14778-93855 Tehran, Iran.</span></i></span></span></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div>
<br><div class="gmail_quote">On Thu, Nov 17, 2016 at 2:16 PM, Giovanni Cantele <span dir="ltr"><<a href="mailto:giovanni.cantele@spin.cnr.it" target="_blank">giovanni.cantele@spin.cnr.it</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word">No, it is not necessary if you do not expect that the system under study has a magnetisation.<div>See here:</div><div><a href="http://www.quantum-espresso.org/wp-content/uploads/Doc/pw_user_guide/node10.html#SECTION00043030000000000000" target="_blank">http://www.quantum-espresso.<wbr>org/wp-content/uploads/Doc/pw_<wbr>user_guide/node10.html#<wbr>SECTION00043030000000000000</a></div><div><br></div><div>In practice, for solids where NO internal or external magnetic field is not present,</div><div>time-reversal symmetry applies. This has the consequence that</div><div><br></div><div>E(k,up) = E(-k,down)</div><div><br></div><div>so for a non-magnetic solid, even in the presence of spin-orbit coupling, it is possible that the spin-up and spin-down</div><div>densities are the same and the total magnetisation zero. Non-magnetic solids then can divided into</div><div>systems with (spatial) inversion symmetry and systems where this symmetry does not apply.</div><div><br></div><div>The former have the additional constraint that E(k, any_spin)=E(-k,any_spin) that, combined with the previous equation,</div><div>produces double SPIN degenerate bands (so each state AT GIVEN is at least double degenerate). Germanium is an example.</div><div><br></div><div>The latter show a lifting of this double SPIN degeneracy, like in the case of GaAs. The spin degeneracy is recovered ONLY</div><div>for those k-points for which k and -k are equivalent (thus differing by only a reciprocal lattice vector). Gamma point is an example.</div><div><br></div><div>Giovanni</div><div><br></div><div><br><div><blockquote type="cite"><div><div class="h5"><div>On 16 Nov 2016, at 22:17, ashkan shekaari <<a href="mailto:shekaari@gmail.com" target="_blank">shekaari@gmail.com</a>> wrote:</div><br class="m_-2311156893391656369Apple-interchange-newline"></div></div><div><div><div class="h5"><div dir="ltr"><div><div>Dear experts,<br><br></div>Is starting magnetization necessary to have a full spin-orbit coupling?<br><br></div>What value should it take on?<br clear="all"><div><div><div><div><div class="m_-2311156893391656369gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div><span><span style="background-color:rgb(255,255,255)"><b>--</b></span></span></div><div><span><span style="background-color:rgb(255,255,255)"><i style="font-size:12.8px">Regards,</i></span></span></div><div><span><span style="background-color:rgb(255,255,255)"><i>Ashkan Shekaari</i></span></span></div><div><span><span style="background-color:rgb(255,255,255)"><i>Plasma Physics Research Center</i></span></span></div><div><span><span style="background-color:rgb(255,255,255)"><i style="font-size:12.8px"><span style="font-size:12.8px">Science and Research Branch</span></i></span></span></div><div><span><span style="background-color:rgb(255,255,255)"><i>I A U, <span style="font-size:12.8px">14778-93855 Tehran, Iran.</span></i></span></span></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div>
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-- <br><br>Giovanni Cantele, PhD<br>CNR-SPIN<br>c/o Dipartimento di Fisica<br>Universita' di Napoli "Federico II"<br>Complesso Universitario M. S. Angelo - Ed. 6<br>Via Cintia, I-80126, Napoli, Italy<br>e-mail: <a href="mailto:giovanni.cantele@spin.cnr.it" target="_blank">giovanni.cantele@spin.cnr.it</a><br>Phone: +39 081 676910<br>Skype contact: giocan74<br><br>ResearcherID: <a href="http://www.researcherid.com/rid/A-1951-2009" target="_blank">http://www.researcherid.com/<wbr>rid/A-1951-2009</a><br>Web page: <a href="http://people.na.infn.it/~cantele" target="_blank">http://people.na.infn.it/~<wbr>cantele</a><br>
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