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[Emmanuel Arras <emmanuel.arras@cea.fr>]

Are you sure your structure (full input) is correct? It seems it is 
indeed not compatible with antiferromagnetic symetry. Moreover, the 
interatomic distances seem a bit short (less than 1 Anström for Mn-O 
Bond...).


Skorlans Mathew a écrit :
> Dear Users,
>
>   I am trying to optimize the lattice constant for cubic YMnO3 in Para, Ferro
> and Antiferro phases. I could get nice optimization of acell for Para and 
> Ferro
> phases. But, When I tried to optimize the Antiferro phase, I got the following
> error message: Intially, I tried to double the other Mn position, then tried 
> to
> increase by 50% for both cases i was getting same error. But When I gave the
> following positions for Mn (which actually is not the correct one)
>     Mn 0.25 0.25 0.25
>         0.75 0.75 0.75
> It works, I do not know why? Because these positions are not the correct ones.
>
> Here is the ERROR message:
>   
> hkinp: ERROR -
>   When nsppol==1 and nspden==2, at least one of the symmetry operations
>   must be anti-ferromagnetic (symafm=-1), in order to deduce the spin-down
> density
>   from the spin-up density.
>   However, it is observed that none of the symmetry operations is
> anti-ferromagnetic.
>   Action : Check the atomic positions, the input variables spinat, symrel,
> tnons, symafm.
>            In case your system is not antiferromagnetic (it might be
> ferrimagnetic ...),
>            you must use nsppol=2 with nspden=2 (the latter being the default
> when nsppol=2).
>
>    Please, let me know what is wrong with my input file given below:
>
> # Optimization of latice constant for cubic YMnO3 with Spin polarized 
> #(Ferromagnetic) conditions
> ndtset 1
> #Optimization of the lattice parameters
>  
> optcell 1
> ionmov 3
> tolmxf 5.0d-4
> dilatmx 1.1
> ecutsm 0.5
> nband 64 
> nsppol 1
> nspden 2
> nspinor 1
> spinat 0 0 0
>        0 0 0
>        0 0 -4
>        0 0 4 
>        0 0 0
>        0 0 0
>        0 0 0
>        0 0 0
>        0 0 0
>        0 0 0
>
> #Definition of the k-point grids
> kptopt 1  
> nshiftk 1
> shiftk 0.0 0.0 0.0 
> ngkpt1 6 6 6
> getwfk -1  
>
> #Definition of the unit cell
>
> acell 3*3.90 angstrom
>
> rprim 
> 1 0 0 
> 0 1 0 
> 0 0 1
>
> #Definition of the atom types
> ntypat 3 
> znucl 39 25 8
> #ziontypat 11 15 6 
>
> #Definition of the atoms
> natom 10 
> typat 1 1 2 2 3 3 3 3 3 3 # 1=Y 2=Mn 3=O
> xred 0.00 0.00 0.00 #Y 
>      0.25 0.25 0.25   #Y
>      0.50 0.50 0.50  #Mn
>      0.75 0.75 0.75  #Mn
>      0.50 0.50 0.00  #O 
>      0.75 0.75 0.00 #O
>      0.50 0.00 0.50 #O
>      0.75 0.00 0.75 #O 
>      0.00 0.50 0.50 #O
>      0.00 0.75 0.75 #O 
> #Definition of the planewave basis set
> ecut 30.0 
> #Definition of the SCF procedure
> nstep 500 
> toldfe 1.0d-6
> diemac 2.0	  
>
> Thanks and regards
> SKORLANS K M (MS Student)
> Dept.of Physics National Institute os technology India
>
>