Query Regarding Discrepancy in Tc Calculation of CrI3

[Shubrat Singh]

Dear Vampire Community,

I have been working on calculating the Curie temperature (Tc) using the TB2J data provided in the following repository: https://github.com/mailhexu/TB2J_examples.git 
I used the input data from the Vampire folder within the repository for calculations using the Vampire package (see attached files). However, I observed a significant discrepancy between the Tc value obtained from my calculation and the previously reported value of approximately 45 K. I am using the latest version of Vampire package (Software version 7.0). 

I would like to seek clarification on the following points:

1.    What could be the possible reasons behind this discrepancy? Should I have to multiply by factor 2?
2.     Do I need to modify any parameters or settings in the attached input file to obtain consistent results?
3.     Is there any recommended workflow or specific convergence settings to achieve accurate Tc estimation?

Notably, Vampire utilized the UCF file, which includes J_anisotropic and DMI terms, so that the calculated Tc already accounts for J_isotropic, J_anisotropic, and DMI together. 

Your guidance would be greatly appreciated, as it will help me ensure the correctness of my calculations.

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Best Regards

Zimmi Singh

Research_Scholar

Department of Metallurgical and Materials Engineering
Indian Institute of Technology, Kharagpur
Kharagpur, India

[Xu He]

Hello, 

I am a TB2J developer and there are a few things to clarify. 

The TB2J_examples are for showcasing the usage of the TB2J code (the procedure, the syntax, etc). The results are not meant to be used in production. In practice, the result can be very sensitive to the different approximations like the exchange-correlation functionals, DFT+U, etc.  And for 2D materials, the anisotropy is quite important in the computing of the Tc, which is missing in the current version of TB2J. 

There is no need to multiply by 2 to convert between the conventions in TB2J and Vampire. This is done automatically within TB2J. 

Best regards, 

Xu He

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