Dear Giovanni Cantele, Thank you so much for the detailed response. As my last question, what is the exact difference between starting magnetization and total magnetization?
*--* *Regards,* *Ashkan Shekaari* *Plasma Physics Research Center* *Science and Research Branch* *I A U, 14778-93855 Tehran, Iran.* On Thu, Nov 17, 2016 at 2:16 PM, Giovanni Cantele < [email protected]> wrote: > No, it is not necessary if you do not expect that the system under study > has a magnetisation. > See here: > http://www.quantum-espresso.org/wp-content/uploads/Doc/pw_ > user_guide/node10.html#SECTION00043030000000000000 > > In practice, for solids where NO internal or external magnetic field is > not present, > time-reversal symmetry applies. This has the consequence that > > E(k,up) = E(-k,down) > > so for a non-magnetic solid, even in the presence of spin-orbit coupling, > it is possible that the spin-up and spin-down > densities are the same and the total magnetisation zero. Non-magnetic > solids then can divided into > systems with (spatial) inversion symmetry and systems where this symmetry > does not apply. > > The former have the additional constraint that E(k, > any_spin)=E(-k,any_spin) that, combined with the previous equation, > produces double SPIN degenerate bands (so each state AT GIVEN is at least > double degenerate). Germanium is an example. > > The latter show a lifting of this double SPIN degeneracy, like in the case > of GaAs. The spin degeneracy is recovered ONLY > for those k-points for which k and -k are equivalent (thus differing by > only a reciprocal lattice vector). Gamma point is an example. > > Giovanni > > > On 16 Nov 2016, at 22:17, ashkan shekaari <[email protected]> wrote: > > Dear experts, > > Is starting magnetization necessary to have a full spin-orbit coupling? > > What value should it take on? > *--* > *Regards,* > *Ashkan Shekaari* > *Plasma Physics Research Center* > *Science and Research Branch* > *I A U, 14778-93855 Tehran, Iran.* > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum > > > -- > > Giovanni Cantele, PhD > CNR-SPIN > c/o Dipartimento di Fisica > Universita' di Napoli "Federico II" > Complesso Universitario M. S. Angelo - Ed. 6 > Via Cintia, I-80126, Napoli, Italy > e-mail: [email protected] > Phone: +39 081 676910 > Skype contact: giocan74 > > ResearcherID: http://www.researcherid.com/rid/A-1951-2009 > Web page: http://people.na.infn.it/~cantele > > > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum >
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