Dear Prof. Postnikov, I have finished the calculation of the exchange integral of CdFe2O4. But the result shows that the difference between antiferromagnetic structure and the ferromagnetic one is smaller than that from the reference calculating by VASP.
Could you give me some suggestion? FM AFM1 AFM2 AFM3 Total energy (eV) -32369.488809 -32369.715090 -32369.723333 -32369.824269 Delta E 0.33546 0.10918 0.10094 0.00000 Delta Eb 2.71 0.20 0.95 0 Plus Ub 0.76 0.15 0.27 0 b. from Cheng, PRB. 78. 132403, GGA+U Best regard, On Mon, Jul 26, 2010 at 9:59 PM, Bin Shao <[email protected]> wrote: > Dear Prof. Postnikov, > > I have found the swith *MullikenInSCF, thank you all the same*. > > Best, > > > On Mon, Jul 26, 2010 at 9:43 PM, Bin Shao <[email protected]> wrote: > >> Dear Prof. Postnikov, >> >> I set WriteMullikenPop 1 and I can check the Mulliken charges following >> the instruction in your lecture after the calculation finished. I found the >> magnetic moment raise from the 3d electrons in the Fe atom as expect. >> >> But I still don't know how to check the Mulliken charges when the job is >> running and further judge the convergence of the calculation, since I can >> not find anything about the Mulliken charges in the output file in the >> process. >> >> Thank you in advance! >> >> Best regards, >> >> >> On Mon, Jul 26, 2010 at 4:23 PM, Bin Shao <[email protected]> wrote: >> >>> Dear Prof. Postnikov, >>> >>> Thank you for your suggestion and the excellent lecture is what I need >>> now, thank you very much! >>> >>> Best regards, >>> >>> >>> On Mon, Jul 26, 2010 at 3:35 PM, <[email protected]> wrote: >>> >>>> >>>> > >>>> >>it is normal that as you increase your system to include many >>>> >> >equivalent (or almost) atoms >>>> > >>>> > I do not understand why many equivalent atoms will affect the >>>> convergence. >>>> >>>> Hi, >>>> >>>> I explained it already: >>>> >> because of electrons flopping between nearly degenerate states. >>>> In other words, the states just under the Fermi energy can be >>>> occupied in different way, and the electrons are just shifted around, >>>> without reaching the convergence. >>>> >>>> >>To get an idea, look at the results (Mulliken charges; DOS) >>>> >> >underway, after some number of iterations. >>>> > >>>> > Could you give me some ditails about checking the results of Mulliken >>>> > charges or DOS after some number of iterations? >>>> >>>> You print out Mulliken charges, there is a switch for it. >>>> You look at them and think whether they are as you expect >>>> (i.e., the atoms which ought to be magnetic are magnetic, >>>> and in a right way). >>>> Check if you find anything useful in the following lecture: >>>> >>>> http://www.home.uni-osnabrueck.de/apostnik/Lectures/APostnikov-Magnets.pdf >>>> >>>> > Usually, I just check the following information of the scf. >>>> >>>> >--------------------------------------------------------------------------- >>>> > siesta: iscf Eharris(eV) E_KS(eV) FreeEng(eV) dDmax Ef_up >>>> > Ef_dn(eV) >>>> > ...... >>>> > siesta: 799 -32180.0924 -32180.0919 -32180.0919 0.0011 >>>> -3.0670 >>>> > -3.0670 >>>> > siesta: 800 -32180.0924 -32180.0919 -32180.0919 0.0011 >>>> -3.0670 >>>> > -3.0670 >>>> ... >>>> > siesta: 826 -32180.0929 -32180.0925 -32180.0925 0.0010 >>>> -3.0669 >>>> > -3.0669 >>>> > siesta: 827 -32180.0931 -32180.0927 -32180.0927 0.0010 >>>> -3.0668 >>>> > -3.0668 >>>> > ...... >>>> >>>> This is good but does not tell you anything but that your calculation >>>> is not quite converged. >>>> In fact it doesn't look like a divergence, and the Fermi level(s) are >>>> not a priori unreasonable. So, before doing anything else, try >>>> to make sense out of your calculation (position of bands, magnetic >>>> moments, etc.) >>>> >>>> >>>> ---------------------------------------------------------------------------- >>>> > >>>> > I'd like to increase the DM.MixingWeight to 0.3 to accelerate the >>>> > calculation. Is it correct? >>>> >>>> If it smoothly converges to a right solution, that's fine. >>>> But I'd rather suggest, with system as large as yours, to be >>>> more prudent. 0.3 is a huge mixing weight. >>>> >>>> > Since you said I need a small mixing >>>> > parameter, >>>> > how to understand the mixing parameter? I read some notes about >>>> > DM.MxingWeight, but there is still something puzzled me. >>>> > >>>> > alpha has to be small (0.1-0.3) for insulator and semiconductors, >>>> > tipically much smaller for metals. >>>> >>>> Yes; what is the problem? In metals you need a good sampling of states >>>> near the Fermi level; imagine you have a narrow band which shifts >>>> across the E_f; then you'd like to damp the resulting fluctuations. >>>> In semiconductors the situation is (usually) less critical because >>>> bands are either occupied or empty. >>>> >>>> > BTW, whether my setting of the antiferromagnetism is correct. >>>> >>>> I don't know the structure, sorry. Apart from this - yes; >>>> some Fe atoms marked "+" and others "-", as it should be. >>>> >>>> Best regards >>>> >>>> Andrei Postnikov >>>> >>>> >>> >>> >>> -- >>> Bin Shao >>> College of Information Technical Science, Nankai University >>> 94 Weijin Rd. Nankai Dist. Tianjin 300071, China >>> Email: [email protected] >>> >> >> >> >> -- >> Bin Shao, Ph.D. Candidate >> >> College of Information Technical Science, Nankai University >> 94 Weijin Rd. Nankai Dist. Tianjin 300071, China >> Email: [email protected] >> > > > > -- > Bin Shao, Ph.D. Candidate > College of Information Technical Science, Nankai University > 94 Weijin Rd. Nankai Dist. Tianjin 300071, China > Email: [email protected] > -- Bin Shao, Ph.D. Candidate College of Information Technical Science, Nankai University 94 Weijin Rd. Nankai Dist. Tianjin 300071, China Email: [email protected]
