[Pw_forum] Non-collinear calculations: magnetic moment relaxation

Gabriele Sclauzero sclauzer at sissa.it
Wed Dec 1 10:33:23 CET 2010

Dear Pavel,

   at a first glance, it looks to me that your degauss is to large and the k-point sampling insufficient for magnetic calculations. This said, I don't understand why you get such a strange solution. With your initial choice of the angles you might be forcing some symmetry that prevents from reaching the ground state. Nevertheless, if you start from a magnetic configuration very far from the ground state you might get trapped in some local minima even with the correct symmetry, I suppose. 

Beware that starting_magnetization should be between -1 and 1, see Doc/INPUT_PW.txt. 
I remember that Paolo put some checks at some point. Which version of the code are you using?

Finally, unless you include spin-orbit coupling or you consider situations with frustrated magnetism there is no need of using the noncollinear scheme.



Il giorno 01/dic/2010, alle ore 02.49, Lukashev Pavel ha scritto:

> Dear All,
> I am running a test calculation of bcc iron, to check if the relaxation of angle1 (theta) works correct for the non-collinear case. I have copied the file "fe.pen.in" from the examples provided on pwscf.org, and added one more Fe atom (so, I have two Fe atom unit cell). I set angle1(1)=90;  angle1(2)=0.0. After self-consistent calculation I expect these angles to be aligned (ferromagnetically). Yet, I end up getting very strange result, i.e. theta(1)=70.356498; theta(2)=19.684944. Does this mean that the relaxation of atomic magnetic moments is not very reliable in case of non-collinear calculation? This is first time I am trying to include non-collinearity in my calculation, therefore I don't have much to compare with. And I did not find any published work on non-collinear systems done with PWSCF. Any help on this issue is very appreciated. I attach my input file which also includes portion from output showing magnetization magnitude/direction.
> Sincerely,
> Pavel Lukashev, Ph.D.
> Research Associate
> UNL, Department of Physics & Astronomy
> 208 Theodore Jorgensen Hall
> 855 N. 16th Street
> Lincoln, NE 68588-0299
> Office: (402) 472-2400
> <Fe-noncollinear.txt>_______________________________________________
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> Pw_forum at pwscf.org
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§ Gabriele Sclauzero, EPFL SB ITP CSEA
   PH H2 462, Station 3, CH-1015 Lausanne

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