Hi Gabriele, I am sorry. Before, there are usually the words "spin up" and "spin down" in the spin polarization cases. I did not see it this time, so I thought something was wrong here. When I looked at the band data again, I saw the number of eigen values are double there, which means one for each spin state. So I saw it now. I am sorry for my bad.
Thanks, Trinh > Dear user, > > vtmtrinh at caltech.edu wrote: >> Dear PWSCF Users, >> >> Does any of you know how to calculate spin splitting using QE? More >> clearly, if I have 2 structures (Si 8-atom cell), one at equilibrium and >> the other one with atoms being displced according to phonon mode. I >> would >> like calculate the energies of the spin up and down. There are 2 >> concerns > > You did not clarify much, in my poor understanding. What do you want to > calculate? The > splittings between the spin up/spin down eigenvalues? > That should be easy, you do a calculation with nspin=2 and a guess for the > starting > magnetization and, if your system stays magnetic, you can easily compute > the splittings > from the list of eigenvalues given on output at the end of the > calculation. > > Or maybe you want to compute total energy difference between an AF and a > FM configuration? > > Why do you mention two configurations that differ by atomic displacements > and ask about > computing spin up/spin down splittings? Does magnetism arise in the second > case due to the > displacement from equilibrium configuration? > > >> that I have: (i) The difference in eneries for these 2 states is too >> small. Can we get to that level of accuracy by using QE. > > It depends what is the accuracy you need. In principle you can increase it > by increasing > PW/charge-density cutoffs, number of k-points, and decreasing degauss (you > may also need > to decrease conv_thr or other things that did not come in my mind in this > moment...). Then > you probably have to face with the error due to the use of > pseudo-potentials, but > generally the error in energy differences can be believed to be lower than > absolute error > on the total energies. > > (ii) how to do >> it (how to fix spin up and down). > > I don't understand exactly what you want to fix. You can for instance fix > the total spin > magnetization of your system using the tot_magnetization or multiplicity > variables. > > HTH > > GS > > >> >> Any suggestion would be appreciated. >> >> Thank you, >> >> MyTrinh Vo >> >> Computation group >> JPL/CalTech >> >> _______________________________________________ >> Pw_forum mailing list >> Pw_forum at pwscf.org >> http://www.democritos.it/mailman/listinfo/pw_forum >> > > -- > > > o ------------------------------------------------ o > | Gabriele Sclauzero, PhD Student | > | c/o: SISSA & CNR-INFM Democritos, | > | via Beirut 2-4, 34014 Trieste (Italy) | > | email: sclauzer at sissa.it | > | phone: +39 040 3787 511 | > | skype: gurlonotturno | > o ------------------------------------------------ o > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum >
