The simulation of the paramagnetic state (according to P Blaha reply )

[Wien] please help

Peter Blaha Wed, 17 Sep 2008 10:46:52 +0200

As I said in my previous mail:

A paramagnetic state of a 4f compound does NOT mean that one should do a
unpolarized calculation.
Even in the paramagnetic case, one has local moments on each Gd site, but
they are no longer long range ordered, but randomly oriented, thus there
is no net magnetization.

Eventually you can try the effects of magnetic disorder and flip the spins
on two Gd atoms in your supercell (so that the net moment of the cell is again
zero, but you do not have the strict AF state anymore.

Reference: https://www.mail-archive.com/wien%40zeus.theochem.tuwien.ac.at/msg01133.html

[Wien] Calculation of properties by wien2k for other than zero K

Peter Blaha Sun, 21 Mar 2010 10:33:16 +0100


"nonmagnetic" is a sloppy term.  ferromagnetic, disordered, paramagnetic or 
diamagnetic is much more precise.
A "ferromagnetic" material usually does NOT loose its LOCAL magnetic moment 
above Tc, but the moments are no longer long range ordered, but get disordered.

Thus in most cases even above Tc a "ferromagnetic" calculation is a much better
approximation than a "nonmagnetic" one !!

The best you could do, is to create a large supercell, put some moments on each
atom with "random" spin-up/dn orientation such that the total moment of the cell
is zero. This corresponds to a "disordered local moment" model of a ferromagnetic
solid above Tc.

In addition you may select TEMPerature broadening with the appropriate 
temperature.

Reference: https://www.mail-archive.com/wien%40zeus.theochem.tuwien.ac.at/msg02457.html