Thanks a lot for your help. Also, I have another question. How is the spin-orbit implemented in QE, i.e. is there any approximation. In other words, could you give me the ref that QE is based on (if any). I am looking for the part of the code that ralted to the spin-orbit, but so far, I still could not locate it. I appreciate if you could let me know.
Best, MyTrinh > > > vtmtrinh at caltech.edu wrote: >> Hi Gabriele, >> >> Thanks for your reply. I am sorry for the unclear question. >> The question is to calculate the splitting between the spin up and spin >> down states in the conduction band (CB) of Si. For equlibrium Si bulk, >> there should be no spin splitting. Therefore, the splitting can be >> induced >> by moving the atoms a long phonon modes. The spin splitting is probably >> of >> the order ~1e-7eV. >> >> Yes, you are right. I need to set nspin=2. Since I also need to >> include >> the spin-orbit coupling in this calculation, I have to use >> noncolinear=.true. > > Now the situation is much more clear :-) > > >> >> I run a calculation yesterday, in which I set lspinorb=.true. and >> noncolinear=.true. By setting this I think that spin-polarized >> calculation >> was aslo done. However, in the output, I don't see the eigen values for >> spin up and spin down, but only one (like for the non-polarization >> case). > > You're right, in a noncolinear calculation you don't see SPIN UP and SPIN > DOWN bands as in > a LSD calculation. > Anyway, as you also noticed, the number of bands is doubled when you set > noncolin=.true. > If you don't include SO coupling, you should get (for each band of the non > spin-polarized > calculation) a spin up and a spin down band which coincide with those > obtained with a > collinear LSD calculation (i.e. with noncolin=.false., nspin=2). Also the > final total > magnetization should be the same (you can check from the output). > You can plot the bands (for instance using bands.x and then plotband.x) > and compare the > splittings. > When you include SO the situation is more complicated (you should label > your bands with > the irreps of the (magnetic) double group of the system), but in principle > more close to > reality. > You can plot bands also in this case and see what changes and how much > (tyr lsym=.true. > when running bands: it can label bands according to the irreps and it may > be very useful). > The SO splitting would be small, though. In the Si atom the SO splitting > of 3p electrons > should be of the order of few mRy (which is only slightly larger than the > error from PPs, > so be careful...), and in the bulk they are usually lower. > > > Cheers, > > GS > > >> I am not sure if I did not set the right parameters. Attached is my >> input. Could you let me know what wrong with it. >> >> Thanks, >> >> MyTrinh >> > -- > > > 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 >
