[QE-users] How can we decide the spin state of the relaxed structure

[Andrii Shyichuk]

Dear Naga, 

1. The starting magnetization result is weird. 
There are apparently a few areas/centers of magnetization, summing up to
2.77 absolute magnetization.
Some of them are up, and some of them are down, hence the total
magnetization (spin up minus spin down) is 0.3.

Plot the magnetization to see what happens, while atomic magnetizations
can be found in the output file, after the SCF steps.
Same goes for the other results. Without the magnetization plot, you
cannot know if it is localized where it should be. 

I assume that there is only one Co atom in the system, and the
magnetization should be localized there. 
In the starting magnetization result, it is not. 

2. The triplet state has a lower energy, so yes, it looks more stable.
Is it also more stable in the experimental data?

3. I'd say, the better approach is the one giving you a reasonable
result.
The tot_magnetization calculations are stable in a sense that they are
likely to converge with the desired magnetization.
The starting_magnetization are less stable from my experience: low-spin
states can converge from high-spin starting_magnetization. 

Best regards.
Andrii Shyichuk

W dniu 2020-10-21 09:52, samala nagaprasad reddy napisał: 

> Hello QE experts, 
> 
> I am trying spin polarized DFT studies of Co-corrole complex using QE (using just gamma point and large box size to avoid interactions),  I am relaxing the structure using  nspin = 2 and  starting_magnetization(6) = 1.0, as initial guess of Co atom. At the end of relaxation I have observed the below 
> 
> total magnetization       =     0.31 Bohr mag/cell
> absolute magnetization    =     2.77 Bohr mag/cell 
> and Final energy   =   -1144.9536036757 Ry 
> 
> When I minimize the structure in singlet and triplet states by fixing the total magnetization (non spin polarized gives singlet state, and used tot_magnetization = 2 for triplet). The relaxed energies are 
> Final energy   =   -1144.9318071744 Ry  (singlet) 
> Final energy   =   -1144.9537812641 Ry  (triplet) 
> 
> Regarding this I have few queries 
> 1) what is the spin state of the relaxed complex with starting_magnetization(6) = 1.0 (singlet/triplet or any other)? It seems the electronic spin state is singlet bec the total magnetization is 0.31 and is close to 0. 
> 2) In the spin restricted calculations, the triplet state is more stable than the singlet and how can we understand it from the above? 
> 3) which approach is better (whether the guess starting_magnetization or by fixing the total magnetization)? 
> 
> Thanks in advance 
> Naga 
> 
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu [1])
> users mailing list users at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users

  

Links:
------
[1] http://www.max-centre.eu
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20201021/c9af2e61/attachment.html>