Re: [Wien] What's the difference between the spin-polarized and the non spin-polarized calculations
Thank you Dr Gavin and Dr Gerhard for your answers. The were really very fruitful for me. We can consider that the non spin-polarized is a special case of the spin-polarized case. therefore we can use the equations of the general case to get the equations of the special case. So we can make B_eff = 0 to get the non-polarized case, and the results will be different as the energies. another question: How can explain that at the level of the paired and unpaired electrons? Will we force the unpaired electrons to be paired one or something other ? Thank you for your interesting -- Mr: A.Reggad Laboratoire de Génie Physique Université Ibn Khaldoun - Tiaret Algerie ___ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
Re: [Wien] What's the difference between the spin-polarized and the non spin-polarized calculations
I guess the answer is basic calculus B_eff = V_up - V_dn is zero when V_up = V_dn and the equations in the spin polarized and the non spinpolarized case become the same, isn't it. (Note: V_up=V_up(rho_up) and V_dn=V_dn(rho_dn) is used for short, the densities rho_up and rho_dn are calculated from the Kohn-Sham wave functions the V(rho) depend on the used exchange-correlation functional.) Just take a pencil and write down the equations given in the trancparencies or textbooks and proof that I am right by setting B_eff=0. ... or you finally did not understand what a selfconsistent field calculation means, then you have to attend some basic courses on mathematics or theoretical physics. Ciao Gerhard DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy: "I think the problem, to be quite honest with you, is that you have never actually known what the question is." Dr. Gerhard H. Fecher Institut of Inorganic and Analytical Chemistry Johannes Gutenberg - University 55099 Mainz and Max Planck Institute for Chemical Physics of Solids 01187 Dresden Von: Wien [wien-boun...@zeus.theochem.tuwien.ac.at] im Auftrag von Gavin Abo [gs...@crimson.ua.edu] Gesendet: Donnerstag, 20. Oktober 2016 07:30 An: A Mailing list for WIEN2k users Betreff: Re: [Wien] What's the difference between the spin-polarized and the non spin-polarized calculations You likely have to derive the Kohm–Sham equations and solve them for the wavefunction solutions (and look into the WIEN2k source code) for the detailed answers to your questions. I haven't done it myself, so I cannot help you there. I think the go to references for that were: Planewaves, Pseudopotentials and the LAPW Method by David J. Singh and Lars Nordström [ http://link.springer.com/book/10.1007%2F978-0-387-29684-5 ] http://www.wien2k.at/reg_user/textbooks/double_counting.pdf http://www.wien2k.at/reg_user/textbooks/DFT_and_LAPW_2nd.pdf My attempt at general answers: No parameters are monitored to make the 2 densities equal. As seen on slide 21 of http://www.wien2k.at/events/ws2015/rolask_rela.pdf , there are two equations, one for Psi_up and one for Psi_down, but for the non-spin polarized case both equations are the same such that Psi_up = Psi_down = Psi. So only one equation for the wavefunction Psi needs to be solved for. As seen on slide 66 in http://www.wien2k.at/events/ws2015/WS22-KS-DFT-LAPW.pdf , the calculation is given an initial charge density (during init_lapw), then the charge (and spin) density should be computed from the self consistent field (scf) cycles (run_lapw). On the other hand, the spin-polarized calculation (runsp_lapw) has to solve two separate equations instead of one as shown on slide 24 in rolask_rela.pdf. Which is why for example there is lapw1 -up and lapw1 -dn for the spin-polarized calculation and only just lapw1 for the non-spin polarized. The simplified equations it uses for the spin-polarized case was made possible by choosing the z-axis for the direction of the magnetic field [ Ab Initio Study of NiO-Fe Interfaces: Electron States and Magnetic Configurations by L. D. Giustino, http://www.nano-phdschool.unimore.it/site/home/phd-students/documento102017667.html (page 24) ]. The Bef term is crossed out on slide 21, so there should be no exchange magnetic potential Bxc, since Bef = Bext + Bxc (from slide 19). However, whether Bef term is not there or how the Bef term is set to 0, I don't know and someone else might; I didn't look into the source code to try to determine that. On 10/19/2016 5:18 PM, Abderrahmane Reggad wrote: Thank you Dr Gavin for your reply and also for your interesting for my questions. I have checked the 2 presentations but I didn't find what I look for . It's mentionned that in non spin-polarized calculation the spin-up density = the spin-down density . Which parameters are they monitored to make these 2 densities equal. I have read that in this case the exchange magnetic potential will be equal to zero. I want to know if it's so or not . Best regards -- Mr: A.Reggad Laboratoire de Génie Physique Université Ibn Khaldoun - Tiaret Algerie ___ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
Re: [Wien] What's the difference between the spin-polarized and the non spin-polarized calculations
You likely have to derive the Kohm–Sham equations and solve them for the wavefunction solutions (and look into the WIEN2k source code) for the detailed answers to your questions. I haven't done it myself, so I cannot help you there. I think the go to references for that were: Planewaves, Pseudopotentials and the LAPW Method by David J. Singh and Lars Nordström [ http://link.springer.com/book/10.1007%2F978-0-387-29684-5 ] http://www.wien2k.at/reg_user/textbooks/double_counting.pdf http://www.wien2k.at/reg_user/textbooks/DFT_and_LAPW_2nd.pdf My attempt at general answers: No parameters are monitored to make the 2 densities equal. As seen on slide 21 of http://www.wien2k.at/events/ws2015/rolask_rela.pdf , there are two equations, one for Psi_up and one for Psi_down, but for the non-spin polarized case both equations are the same such that Psi_up = Psi_down = Psi. So only one equation for the wavefunction Psi needs to be solved for. As seen on slide 66 in http://www.wien2k.at/events/ws2015/WS22-KS-DFT-LAPW.pdf , the calculation is given an initial charge density (during init_lapw), then the charge (and spin) density should be computed from the self consistent field (scf) cycles (run_lapw). On the other hand, the spin-polarized calculation (runsp_lapw) has to solve two separate equations instead of one as shown on slide 24 in rolask_rela.pdf. Which is why for example there is lapw1 -up and lapw1 -dn for the spin-polarized calculation and only just lapw1 for the non-spin polarized. The simplified equations it uses for the spin-polarized case was made possible by choosing the z-axis for the direction of the magnetic field [ Ab Initio Study of NiO-Fe Interfaces: Electron States and Magnetic Configurations by L. D. Giustino, http://www.nano-phdschool.unimore.it/site/home/phd-students/documento102017667.html (page 24) ]. The Bef term is crossed out on slide 21, so there should be no exchange magnetic potential Bxc, since Bef = Bext + Bxc (from slide 19). However, whether Bef term is not there or how the Bef term is set to 0, I don't know and someone else might; I didn't look into the source code to try to determine that. On 10/19/2016 5:18 PM, Abderrahmane Reggad wrote: Thank you Dr Gavin for your reply and also for your interesting for my questions. I have checked the 2 presentations but I didn't find what I look for . It's mentionned that in non spin-polarized calculation the spin-up density = the spin-down density . Which parameters are they monitored to make these 2 densities equal. I have read that in this case the exchange magnetic potential will be equal to zero. I want to know if it's so or not . Best regards -- Mr: A.Reggad Laboratoire de Génie Physique Université Ibn Khaldoun - Tiaret Algerie ___ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
Re: [Wien] What's the difference between the spin-polarized and the non spin-polarized calculations
Thank you Dr Gavin for your reply and also for your interesting for my questions. I have checked the 2 presentations but I didn't find what I look for . It's mentionned that in non spin-polarized calculation the spin-up density = the spin-down density . Which parameters are they monitored to make these 2 densities equal. I have read that in this case the exchange magnetic potential will be equal to zero. I want to know if it's so or not . Best regards -- Mr: A.Reggad Laboratoire de Génie Physique Université Ibn Khaldoun - Tiaret Algerie ___ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
Re: [Wien] What's the difference between the spin-polarized and the non spin-polarized calculations
If you haven't already done so, I suggest looking at and comparing slides 76 and 77 in the WIEN2k presentation "Relativistic effects, non-collinear magnetism (NCM)", which can currently be found at http://www.wien2k.at/onlineworkshop/ Of note, "sp" should be added under the magnetic case on slide 78 so that it looks like slide 21 in the the file at http://www.wien2k.at/events/ws2008/talks/Laskowski-SO-NCM.pdf On 10/18/2016 8:39 AM, Abderrahmane Reggad wrote: Dear wien2k users I have checked many discussions about the difference between the SP and the non SP calculations and I didn't find a sufficient explanation that removes the ambiguity . So I want to know the difference between the 2 calculations at the level of imput and results for a non magnetic system and for a magnetic one. Best explanation I foud up to now is the following link: http://www.southampton.ac.uk/assets/centresresearch/documents/compchem/DFT_L10.pdf Best regards -- Mr: A.Reggad Laboratoire de Génie Physique Université Ibn Khaldoun - Tiaret Algerie ___ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
[Wien] What's the difference between the spin-polarized and the non spin-polarized calculations
Dear wien2k users I have checked many discussions about the difference between the SP and the non SP calculations and I didn't find a sufficient explanation that removes the ambiguity . So I want to know the difference between the 2 calculations at the level of imput and results for a non magnetic system and for a magnetic one. Best explanation I foud up to now is the following link: http://www.southampton.ac.uk/assets/centresresearch/documents/compchem/DFT_L10.pdf Best regards -- Mr: A.Reggad Laboratoire de Génie Physique Université Ibn Khaldoun - Tiaret Algerie ___ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
