Applicability of TB2J for Exchange Coupling Calculations in Lanthanide-Based Systems

[Neeraj Dhauni]

Dear TB2J Developers,

I am new to TB2J and am currently exploring its capabilities for calculating magnetic exchange interactions. While going through the documentation and available examples, I noticed that most of the demonstrated applications involve transition-metal-based magnetic systems (e.g., 3d compounds).

My research interest, however, is focused on lanthanide (4f) systems, where the magnetic interactions are often strongly influenced by localized 4f electrons, strong spin–orbit coupling, and crystal-field effects.

I would therefore like to ask:

Can TB2J be reliably used to calculate exchange coupling parameters for lanthanide-based materials? If so, are there any specific considerations, limitations, or recommended workflows when treating 4f electrons within TB2J?

I would greatly appreciate any guidance or references that could help me get started with exchange calculations for lanthanide-based magnetic systems.

Thank you for your time and assistance.

Best Regards,

Neeraj

[Xu He]

Hello Neeraj, 

The method should work for Lanthanide-Based Systems. The magnetic force theorem works well in the U>>t limit, which is perfect for these systems. 

There are a few things to be noticed:

- The DFT convergence can be very challenging for 4f electrons due to many possible local minima.  

- If you use Wannier functions, the upper 4f electron can be quite high sometimes, making the disentanglement very difficult if not impossible. Tune the parameters carefully to make sure it is converged to the right state. 

Best regards,

HeXu