[Pw_forum] problem to converge using constrained_magnetization

["Alejandro Rébola"]

Dear all,

I'm performing a scf calculation for an AFM structure. I fix the magnetic
moments of the Fe ions using, for instance:

starting_magnetization(1)=0.7
starting_magnetization(2)=-0.7

constrained_magnetization='atomic'

I use the experimental structure of the system and perform a scf
calculation for different magnetic moments (I want to estimate the GS
magnetic moment).

My problem is that the system only converges for one value of the starting
magnetization (0.5) and doesn't converge in all the other cases I've
tried.
According to the pwscf documentation, LAMBDA, the Lagrange multiplier for
the magnetic penalty term, ".. is reduced in the first iterations and is
increased slowly up to the input value." (I've tried LAMBDA=1,10,20,30,50)
Then, could it be that I should use much bigger values for LAMBDA? Is
there a default value for it? I couldn't find it.

Thank you in advance for you help.

Best regards,

Alejandro