Can TB2J Be Used to Compute Exchange Parameters and Curie Temperature for Magnetic Dopants at Different Separations (3–7 Å)/configurations in a 5×5×1 Supercell?

[suraj dhongade]

Hello He Xu,

I am currently studying a hexagonal monolayer oxide system with defects and transition metal dopants using a 5×5×1 supercell approach. My work involves analyzing exchange interactions between two defects/dopants in fully relaxed structures.

From the literature, I observe that exchange parameters are often estimated using the energy difference between ferromagnetic (FM) and antiferromagnetic (AFM) configurations, followed by Curie temperature (Tₙ/Tc) calculations using mean-field approximation or Monte Carlo simulations (e.g., via the VAMPIRE code).

I would like to ask whether it is appropriate to use the TB2J code for such systems to extract exchange parameters for defect- or dopant-induced magnetism in a supercell. If so, can these parameters be reliably used as input for subsequent Curie temperature calculations using VAMPIRE?

I would greatly appreciate your guidance on this approach.

Thank you in advance for your time and help.

Best regards,
Suraj Dhongade,
PhD Scholar,
E&ECE,
IIT Kharagpur,
India

[Xu He]

Hello, 

TB2J is indeed a good choice for studying defects and dopants as it can give the J values with just one DFT SCF calculation, whereas total energy method typically require much heavier calculations. And it can be used with Vampire. 

I would suggest to first compute the exchange parameters in the pristine system in the unitcell, and test the parameters . 

Best regards, 

HeXu

[suraj dhongade]

I really appreciate the response. I would like to mention that the pristine unit cell is a non-magnetic structure, how the exchange parameter mean anything? I am trying to calculate the exchange parameters between two magnetic dopants in 2D materials. 
Please check out this paper
Magnetic order and critical temperature of substitutionally doped transition metal dichalcogenide monolayers
https://doi.org/10.1038/s41699-021-00233-0

Would be waiting for your reply.

Thanks.....

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[Xu He]

Hello, 

Ah. I thought it was a doped magnetic system. 

Yes you can still use TB2J to compute the exchange in these systems if the magnetic moment is localized. If the magnetic moment becomes itinerant the 

Best regards, 

HeXu

[suraj dhongade]

Thanks Hexu…..can you please share few tutorial, please.