How to know if your compound is magnetic or no ? (from wien mailing list )

Qiwen YAO Sat, 10 Mar 2012 00:55:18 +0900

Dear all,
May I ask:

is it correct to assume that the WIEN2k code will Optimizes the spin structure 
of a stucture/cell in ground state if, I choose spin-polarized calculation for 
the structure/cell from the beginning?

What I mean is:
for a compound, I only suspecting that it is magnetic and I have to include 
spin-polarization in the calculation, but I don't know wheather it is 
ferromagnetic, perfect-antiferromagentic or canted antiferromagnetic or even a 
mixed state of the magnetic status, so I would just do a spin-polarized 
calculation (selecting all the atoms in the cell to be spin-up from the 
beginning), then the resulting converged spin state would be the loweset energy 
state of the compound? - if that is a yes then it i
s basically the case that, Wien2k sort it out itself and practically it was an 
Optimized spin structure for the compound in the ground state?

Thank you for your time.

Kind regards,
Qiwen

[Wien] A question regarding magnetic/spin calculation in Wien2k please

Rocquefelte Fri, 09 Mar 2012 17:12:35 +0100

If you start from a ferromagnetic situation, you will converge towards a 
ferromagnetic state (I never encounter other situations).
However, it does not mean that you will find the global minimum in terms 
of magnetic structure.
It simply means that you have converged the electronic density related 
to the ferromagnetic configuration of your system (It will be a local 
minimum - a metastable situation).

To know which magnetic structure is the more stable, you should try 
different magnetic ordering, or at least one ferromagnetic situation and 
few antiferromagnetic situations (if possible). Then by comparing the 
total energy of the different situations you will see which one is the 
more stable.

In the other hand, another way to estimate the magnetic interactions in 
a system is to estimate the magnetic exchange couplings, J(ij), using a 
mapping analysis (based on energy differences between different magnetic 
orders). It will give you the nature of the magnetic interaction in all 
directions and will help you to figure out what is the fundamental 
magnetic state of your system.

Best Regards

Xavier

[Wien] A question regarding magnetic/spin calculation in Wien2k please

Laurence Marks Fri, 9 Mar 2012 11:13:13 -0600

Actually.... I have come across several cases where I started with a
ferromagnetic state and it converged to non-magnetic or even
antiferromagnetic, or the opposite. It does take a long time for it to
change, so as Xavier says it is probably better to start from
different minima.

Note: the atomic positions can couple in to the spin-state, so you may
need to do a full minimization not just a single set of atomic
positions.

Reference/ https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg06341.html