[DFTB-Plus-User] Total energy VS Mermin energy

[toufik esssakhri]

Dear all,

I am interested on determining the magnetic ground state of a magnetic material, I considered FM and AFM alignments. Should I compare the total energies or Mermin free energies?

I am asking because I can see from the manual that “when using a finite temperature, the Mermin free energy (which the code prints) should be used instead of the total energy”.


Total energies :

FM : -95.5814 eV

AM : -95.5830 eV

Total Mermin free energies:

FM : -95.5842 eV

AM : -95.5832 eV


You can notice when comparing total energies FM is the ground state. However, it is AM if we are comparing Mermin free energies.

I am using the MethfesselPaxton filling

Filling = MethfesselPaxton {

Temperature [Kelvin] = 100.0

Order = 1

}


Thank you

Regards,

Toufik

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