The problem of setting of ferromagnetic and antiferromagnetic states

[Bertha_He]

Dear QuantumwiseStaffs:
        My  ATK version is 2016.04.Recently,I began to learn how to use ATK.Now,I am calculating zigzag MoS₂  nanoribbon.I want to know if I need to calculate the zigzag MoS2  nanoribbon about the total energy of a ferromagnetic or antiferromagnetic state,How do I set the nanoribbion to anti-ferromagnetic and ferromagnetic in the Script Generator?   I am looking forward to your reply.Thank you.

[Daniele Stradi]

Dear Bertha_He,

in order to set the FM solution, you should set the spin of the Mo and S atoms to spin = +1, whereas for the AFM solution, you should set the Mo atoms to a spin = +1 and the S atoms to spin = -1. It might be also useful to set the keyword fixed_spin_moment (see e.g. https://docs.quantumatk.com/manual/Types/LCAOCalculator/LCAOCalculator.html#lcaocalculator-c), which allows one to set the total spin moment of the system. For example, for the AFM solution, you should do a spin-polarized calculation with the spin moments set as described above, and set fixed_spin_moment = 0.

Best regards,
Daniele

[Bertha_He]

Dear Daniele，
          Thank you so much for your reply.I want to know,If I want to set the nanoribbon to FM state,should Iset all the sulfur and molybdenum atoms to 1, or should I  just set them to the two zigzag edges?Similarly, the anti-ferromagnetic value should be set for the zigzag edges or for all atoms?
          Once again, I really appreciate your help.

Bertha

[Petr Khomyakov]

I would guess that it really depends on the nature of ferromagnetic and antiferromagnetic states in these nanoribbon.  Probably, you could try different initial states to see which one gives rise to the ground state, i.e., the state with the lowest total energy of the system. These issues are likely to have already been discussed in the literature. So, some literature search might be of help to decide on how to set the initial state.