I need help with the Constrained Magnetic moment calculation in VASP for the h-LuMnO3 system (30 atoms). I should be thankful if anyone has taught me something about this field. I have read many pages about this and they give a few details which I cannot understand correctly (https://www.vasp.at/wiki/index.php/Constraining_local_magnetic_moments). and they gave only for two atoms. If I am doing the same for 30 atoms, what will be the INCAR file of VASP..
First you should specify the magnetic moments for all 30 atoms in the unit cell.
Read more about specifying initial magnetic moments for each atom (MAGMOM); https://www.vasp.at/wiki/index.php/MAGMOM.
Tip:
Make sure you understand the electronic and magnetic structure of your system, so that you have an idea how to initialize the local magnetic moments.
Read more about constraining local magnetic moments using I_CONSTRAINED_M keyword in VASP.
Hope this helps.
Thank you so much Maa'm Gowri Udayangani Kuda Singappulige .
As you said, I have given the MAGMOM for my system, but I am still not getting what the M_CONSTR is or how to give M_CONSTR tag while doing the constrained moment calculations. Please help me to understand this.
I have used the same MAGMOM value for M_CONSTR. What I did is correct or not, but I am not sure. Or else Both MAGMOM and M_CONSTR values are to be different?..
I would be thankful for your reply.
Good question Gowsalya Rajan
MAGMOM keyword is used only to initialize the magnetic moments, that is the initial guess for the magnetic moments to be used at the beginning of the SCF cycle. The local magnetic moments will be optimized during the SCF cycle. The resulting local magnetic moments might be different from the initialized ones.
To constraint the magnetic moments however, I think you should use I_CONSTRAINED_M keyword to decide either to constraint the direction or size and direction. In addition, now you provide the values to be constrained using M_CONSTR keyword.
Hope this is helpful.
Learning with you :)
Gowri
Thank you Maa'm Gowri Udayangani Kuda Singappulige
As of now, I have a clear idea that M_CONSTR is the local magnetic moment that is constrained over the system. So shall I give the moments based on the previous optimized calculations? In OUTCAR I can get the magnetic moments on each atom. I think that will be enough to give in M_CONSTR.
And one more doubt in this calculation is that "RWIGS" is a must for Non-Collinear calculation but I am not sure which value should I give for RWIGS for my system of h-LuMnO3.
Please guide me If I am going in the wrong direction.
Thank you for your conversation with me Maa'm.
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