[Pw_forum] constrained_magnetization

[Lorenzo Paulatto]

In data 03 giugno 2009 alle ore 11:35:06, chu-chun fu <chuchun.fu at cea.fr>  
ha scritto:

> Thank you for your response. Maybe I was not clear enough in my previous
> email. My question is not to give occupation Z to atom X, but local M
> (magnetization) to atom X. My question actually  concerns the 'atomic'
> constrained magnetization option already implemented in PWscf (in
> particular version 4.0.3) by adding a 'penalty functional' as can be
> seen in the SUBROUTINE add_bfield,

Well, yes I mistaken your question a bit, yet that's what constrained DFT  
is about.

> Just wonder if we can only constrain the local magnetization of only one
> species instead of all the atoms to respective values as fixed in the  
> input.

You cannot, but you can assign a different (formally) specie to each atom  
doing something like this:

ATOMIC_SPECIES
  Pd_1  106.40    Pd.pbe-paw_kj.UPF
  Pd_2  106.40    Pd.pbe-paw_kj.UPF
  Pd_3  106.40    Pd.pbe-paw_kj.UPF
ATOMIC_POSITIONS
Pd_1      0.000000         0.000000       0.000000
Pd_2      0.250000        -0.144340       0.408250
Pd_3      0.500000        -0.288680       0.816490

the species will be equivalent in practice, but distinct from the code  
point of view, hence you can assign different constraints to them. It has  
to be done this way because of how the symmetry analysis works: atoms of  
the same specie can in principle occupy equivalent positions, in which  
case it would make no sense to assign different properties to each of them.

best regards


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Lorenzo Paulatto
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