<P>Dear Prof. Stefano de Gironcoli,</P>
<P>Thank you for your detailed reply.</P>
<P>After posting my question, I perform the projwfc calculation.<BR>I found a puzzling relation between the starting magnetization and the resulting polarization (magnetic moment).<BR>I setup the input file as: starting_magnetization(3) = -0.8, and a large value for lambda. In the last iteration pw.x output the following information:<BR> ==============================================================================<BR> atom number 20 relative position : 1.4040 4.1784 9.7071<BR> charge : 7.067449<BR> magnetization : -0.801893<BR> magnetization/charge: -0.113463<BR> constrained moment : -0.800000<BR> ==============================================================================<BR><BR>Now, it was noted that the magnetization is constrained at -0.801893. However, the projwfc calculation gave the results:<BR> Atom # 20: total charge = 16.3788, s = 2.3540, p = 7.1679, d = 6.8569, <BR> spin up = 7.2902, s = 1.1726, p = 3.5766, d = 2.5410, <BR> spin down = 9.0886, s = 1.1814, p = 3.5913, d = 4.3159, <BR> polarization = -1.7983, s = -0.0088, p = -0.0147, d = -1.7748, <BR> ______________<BR><BR>Actually the magnetic moment is -1.7983 (muB?).<BR>I tried the different value of starting_magnetization, and found that the polarization is always about the double of starting_magnetization. So I think the output "magnetization" duing the pw calculation is not the magnetic moment. If the polarized rho is defined as: rho(r)*(1/2+sigma*starting_magnetization), rather than rho(r)*(1+sigma*starting_magnetization)/2, the above relation is reasonable.Am I right?</P>
<P><BR>Best regards</P>
<P>Shujun Hu</P>
<P><BR><BR>>Dr. Shu-jun Hu wrote:<BR>>><BR>>> Dear all,<BR>>><BR>>> I have some qustions about the initio magnetization of ion for LSDA<BR>>> calculation.<BR>>><BR>>> In the input file the "starting_magnetization" is used to break the<BR>>> spin symmetry of magnetic system. By specifying such parameters, how<BR>>> does pw.x initio the magnetic moment of certain ions?<BR>>> Taking transition metal ion Fe for example, if the<BR>>> starting_magnetizaton(Fe)=0.4, how many electrons occupy the spin-up<BR>>> and spin-down channels respectively for the initio wfc? Only the<BR>>> symmetry breaking of 3d electrons are considered in LSDA calculation,<BR>>> or all the valence electrons (both 3d and 4s)?<BR>>><BR>>the starting magnetization variables define the way the initial initial<BR>>charge density, that is used to generate the initial potential, is<BR>>built. The initial density is obtained from the superposition of atomic<BR>>charges, read from the pseudopotential file, and in the case of a spin<BR>>polarized calculation the initial charge density is defined as<BR>>rho(r,sigma) = sum_s=1,Nat rho_at_type(r-Rs) * (1 + sigma*<BR>>starting_magnetization_type)/2<BR>>where sigma is +/- 1 for up/down spin components<BR>><BR>>the atomic charge density is the total one (including the 4s in case of Fe).<BR>><BR>>occupation of the initial wfs is NOT imposed and is the result of the<BR>>first diagomalization + smearing + fermi energy...<BR>><BR>>> Such a question concerns about the output information of calculation<BR>>> with constrained magnetization.<BR>>><BR>>> During the calculation, I got the output information as:<BR>>><BR>>> atom number 14 relative position : 1.4040 4.1784 3.2357<BR>>> charge : 7.082847<BR>>> magnetization : 0.239576<BR>>> magnetization/charge: 0.033825<BR>>> constrained moment : 0.200000<BR>>><BR>>> Does the value of "magnetization" (0.239576) represent the magnetic<BR>>> moment of ion, or the polarization? If the latter case, how to derive<BR>>> the magnetic moment in unit of Bohr?<BR>>><BR>>I may be wrong (I'm not usign this feature often) but inspecting the<BR>>code the meaning of the following output is:<BR>>there are 7.08... electrons in the chosen sphere around the atom # 14<BR>>there are 0.2395... more up electrons than down ones in the sphere...<BR>>this is more the local moment than the local magnetization<BR>>0.033 is the ratio of the two numbers above<BR>>0.20 is the target value of the magnetic moment (the actual value is as<BR>>said 0.2395...). the fact that the actual moment does not agree with the<BR>>target one is due to the fact that the constraint is impose via a<BR>>penalty function. the larger the value of lambda the closer should be<BR>>the computed value to its target.<BR>><BR>>> -------<BR>>><BR>>> Another question is about the total energy given by constrained<BR>>> calculations.<BR>>> I want to compare the total energy of a system with different magnetic<BR>>> moment for certain ions, and find the ground state.<BR>>> In order to fix magnetic moment at the starting value, lambda = 1000<BR>>> is setup. That's a large value.<BR>>> As described in INPUT_PW.html, the penalty energy is introduced at<BR>>> this time. I wonder if the comparison make any sense?<BR>>><BR>>what the code minimizes is the energy including the penalty cost... This<BR>>penalty cost is reported in the output.... I'm not sure however whether<BR>>the printed value of the total energy includes or not this term...<BR>>I hope someone else can comment on that...<BR>><BR>>stefano de Gironcoli<BR>><BR>><BR>>> Any reply to any question is appreciated. If you can also guide me to<BR>>> the position of source code refering to the question, that's great!<BR>>><BR>>> Best regards<BR>>><BR>>> Shujun Hu<BR>>><BR>>> ------------------------------------------------------------------------<BR>>><BR>>> _______________________________________________<BR>>> Pw_forum mailing list<BR>>> Pw_forum at pwscf.org<BR>>> <A href="http://www.democritos.it/mailman/listinfo/pw_forum">http://www.democritos.it/mailman/listinfo/pw_forum</A><BR>>> <BR><BR></P>