thanks for everyone's reply, especially Gabriele Sclauzero's detailed explanation. best regards! graduate student: chen xiaguanying university
?2009-10-02?"Gabriele Sclauzero" <sclauzer at sissa.it> ??? > > >duchl06 wrote: >> hi,Gabriele Sclauzero >> thanks for your advice and hoping your further guide. >> i am reading a paper "Charge-Transfer-Based Mechanism for >> Half-Metallicity and Ferromagnetism in one-Dimensional >> OrganometallicSandwich Molecular Wires" >> http://pubs.acs.org/doi/abs/10.1021/ja804053a >> in this paper they consider a sandwich molecular wires (such as 1D >> (VBz)? wire, (MnCp)? wire, Bz is benzene, Cp** is cyclopentadienyl), and >> they said "Furthermore, we investigate the effect of doubling the unit >> cell size along the SMW direction to evaluate the ground state of >> ferromagnetic (FM), antiferromagnetic (AFM), and diamagnetic (DM) >> con?gurations in our spin-polarized calculations with structural >> optimization, > >In this paper, I think they refer to a non-magnetic ground-state as "DM >configuration". >A priori you do not know if the DFT ground state (which does not necessarily >always >correspond to the true physical GS) will be FM, AFM or non-magnetic. You have >to allow the >system to "explore" an enlarged phase space with non-zero magnetization and >see if the >energy of a magnetic configuration (either FM or AFM) is lower than the >non-magnetic >solution. >Actually, if the GS is non-magnetic, you should end to the non-magnetic GS >even if you >start from a magnetic configuration (unless you get trapped in some local >minimum). >I think that's why \Delta E in table 1 of the paper you pointed out is always >negative (or >not given): if the GS is magnetic, it will have a lower energy than the lowest >energy >non-magnetic solution, otherwise the GS is not magnetic and a spin-polarized >calculation >will give the same GS of a non-spin polarized one. > >HTH > >GS > > > >> and assess possibility of the Peierls transition." >> >> >> (and i also found in some other papers when they do not know the groud >> state is FM or DM, they would always say "To examine the stability of >> the local magnetic state, we calculate the energy difference between the >> diamagnetic and ferromagnetic states". >> >> ?2009-10-02?"Gabriele Sclauzero" <sclauzer at sissa.it> ??? >>> >>> >>>duchl06 wrote: >>>> thanks every one's reply! >>>> hi, Hui Wang >>>> the example you supplied is a calculation for a antiferromagnetic >>>> material, i mean how to set the start magnetic moment for the >>>> diamagnetic material, >>> >>>Diamagnetic material in absence of an external magnetic field should have no >>>net magnetic >>>moment per atom, if I'm not wrong. So it is not clear to me what do you want >>>to study and >>>if all these suggestions are pointing you to the correct solution. If you >>>want to study a >>>diamagnetic material in absence of magnetic field there should be no need >>>for a >>>spin-polarized calculation. >>>So, just to agree on the starting point of your question: what you mean with >>>diamagnetic >>>material is really what people usually refer to? Can you give us more >>>details on the >>>system you want to address? What properties do you want to study? ... >>> >>>Regards, >>> >>> >>>GS >>> > >-- > > >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 -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20091002/e8795759/attachment.htm
