[Pw_forum] Constrained Direction of Magnetization

[Mighfar Imam]

Dear Sahar,
I had similar experience for my system. The
directions of magnetization were changing during
the scf cycles. What i think is that if the gain
in energy as a result of changing the direction
outweighs the energy cost of not respecting the
penalty, the directions will get changed. Also,
the constraint of the magnetization induces a
very strong external magnetic field.
You can try specifying angles without using the
flag "constrained_magnetization".

The radius of the sphere is chosen to be a
little smaller (i.e., divided by 2*1.2) than the
minimum distance (between two atoms in your
system). See PW/make_pointlists.f90

Hope it helps,

Mighfar Imam
JNCASR,
Bangalore, India.



> Hi pwscf users,
> I am trying to do non-collinear calculation
and
> add a penalty functional
> to the Hamiltonian in order to constrain
> direction of magnetic moment of
> some atoms in my desired direction. So I added
> these tags to my usual
> input file:
> noncolin=.TRUE.
> constrained_magnetization='atomic'
> angle1(i)= desired amount in degree
i=1,ntyp
> angle2(i)= desired amount in degree
i=1,ntyp
> lambda=desired amount
> as the result, I expect that the code will
keep
> the direction of magnetic
> moments in desired direction and in every step
> just changes the magnitude
> of magnetization until the convergence
achieves,
> but I see the magnetic
> moment of every atom is changing in both
> magnitude and direction in every
> step.
> 1) Am I missing something in my input file? or
> the whole procedure is
> different from what I expected?
> 2) How starting_magnetization will be related
to
> this constraining
> process?
> 3) How does code choose the radius of the
sphere
> around every atom for
> calculating the charge and magnetic moment of
> every atom?
> I appreciate any help in finding the answers
of
> these questions.
> ______________________________
> Sahar Mirshamsi
> Quantum Theory Project (QTP) and Physics
> Department,
> University of Florida
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum