[Pw_forum] why don't I get an integer magnetization in a finite system

[lfhuang]

Dear E. A. M. Proupin:
>      total magnetization       =     2.79 Bohr mag/cell
Do you expect it to be 4.00 Bohr? If yes, it may be due to the smearing technique you used.  
> In this case, with an even number of electrons, it should be 0, 2, 4, or 2N.
It could also be 0, 0, ...,  or 0 (Bohr), which is dependent on the interaction of electrons in your system. 
> b) smearing.  occupations = 'smearing', smearing = 'cold', degauss = 0.02,
The smearing technique could influence the magnetization moment, you may get more reasonable results by decreasing "degauss" down to 0.005 or lower (even 0.00). 
> And the solution is
> c) tot_magnetization = 2, ! or any even numbe
 It is not different from setting "tot_magnetization = 1.0"  PS: the smearing technique is very helpful in some cases, like optimization of lattice constants, relaxation of atomic positions, reaction-path searching et al., but sometimes, it may not be a good choice in precise description of electronic structures.   
 May these be somewhat helpful.  
Best Wishes! 
Yours Sincerely
L. F. Huang
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L.F.Huang(黄良锋) DFT and phonon physics
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Add: Research Laboratory for Computational Materials Sciences,
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