[QE-users] pw.x - choosing starting_magnetization value for specific expected total magnetization

[Abdul Muhaymin]

Hello QE users,

As I understood that thestarting_magnetization is used to break the spin 
symmetry and can affect the solution. When I did a simple calculation 
changing starting_magnetization, it always converged to the same ground 
state. However, I noticed that for other structures, this is not the 
case. Since there are many local minima, the starting_magnetization 
value determines on what magnetic solution the calculation converges to. 
So my question is then how we should choose it? For example, I am trying 
to simulate a Cu dopant in ZnS. Since Cu2+ has 9 electron in its 3d 
subshell, a neutral dopant then only has 1 unpaired electron. So, should 
I expect 1 Bohr mag/cell? When I set tot_charge=-1 to simulate a charged 
defect, I got everything as 0.0000 as expected since there will be no 
unpaired electron. But simulating the neutral dopant, I am getting 0.00 
total and absolute magnetization. Inspecting the projwfc.x output, I see 
that the dopant atom has 0.0018 polarization. Why is this the case? Why 
not the polarization is 1.00 or close to 1?

My second question is how I can correctly convert my expected 
magnetization to starting magnetization value. For example, if I expect 
the magnetization per cell to be 3 Bohr magneton, what should I choose 
as the starting_magnetization? It seems total magnetization, absolute 
magnetization, polarization etc. are in Bohr magneton unit but not the 
starting_magnetization. I cannot choose starting_magnetization = 3 since 
it should be between -1 to +1. So, how to choose starting_magnetization 
in this case?

Sincerely,
Abdul Muhaymin,
Graduate(MS) Student, Institute of Materials Science and Nanotechnology,
Bilkent University, Ankara