How to do a magnetic calculation?

First of all, we need to do a predictive study to determine if our compound is magnetic or no. a magnetic compound is formed of magnetic atoms like Fe, Mn, Co and Cr but we can get a non magnetic compound formed of magnetic atoms. This predictive study is based upon crystal chemistry. A magnetic compound may be ferromagnetic or antiferromagnetic at ambiant temperature and a magnetic transition may occur for the compound because of apllying temperature or pressure and the new state is called " paramagnetic".

Socondly, in most times we know if our compound is magnetic (ferromagnetic, antiferromagnetic) or non magnetic and we have to prove it by calculation using the suitable method.

Whatever the magnetic nature of our compound, the best and the correct way is to do many calculations for different magnetic configurations (NM, FM and at least 3 AFM configurations). But if we are sure about the magnetic nature of our compound, we may be satisfied with reduced calculations.

If our compound is non magnetic, we can do only a non spin-polarized calculation but it's better to do a spin-polarized calculation and finding a magnetic moment equal to zero to prove that the compound is really a non magnetic one. If the compound is ferromagnetic, it's necessary to do two calculations: a non-spin polarized calculation for non magnetic state a spin-polarized calculation for ferromagnetic state and we have to find that the ferromagnetic state is the most stable. if it's not the case, we have to use another method (GGA ---> GGA+U ) or make a change to our method (increasing U parameter in DFT+U method or increasing the alpha parameter in EECE method) to get the real result. For a antiferromagnetic compound we have to do five calculations as mentionned above (NM, FM and at least 3 AFM configurations). To do a antiferromagnetic calculation click on the following link:

https://wien2k-algerien1970.blogspot.com/2019/01/how-to-begin-to-do-antiferromagnetic.html