nspin and starting_magnetization in Quantum Espresso

Question

In Quantum Espresso, there is a parameter called nspin, which I understand to include in INPUT if there is a paramagnetic species, like $\ce{Fe}$. Thus, we also include starting_magnetization parameter.

I have an $\ce{Fe}$ slab now and require to study adsorption of $\ce{PO4^{3-}}$ (phosphate species) onto the $\ce{Fe}$ slab. Must I include starting_magnetization for $\ce{PO4^{3-}}$? I am assuming that the electronic configurations of $\ce{P}$ ($2\mathrm{p}^3$) and $\ce{O}$ ($2\mathrm{p}^4$) has unpaired electrons, just like $\ce{Fe}$ ($3\mathrm{d}^6$)!

Along with Fe, must I include the parameter starting_magnetization(2) and starting_magnetization(3) for $\ce{P}$ and $\ce{O}$ atoms?

Thanks in advance.

Answer 1

If you anticipate having unpaired electrons, you typically want to initialize those atomic species to have a non-zero magnetization. In some systems, you can initialize the spins to all be 0 and you will still end up with a non-zero magnetization, but in many there’s a local minimum where all of the spins are zero, so if you don’t initialize the spins then you will end up stuck in a state with no net magnetization.