Unrestricted KS?

[simoneca]

Dear all,

I am playing around with spin-polarized calculations and magnetization constraints. I have a background experience with Hartree-Fock calculations, where similarly one can use restricted and unrestricted HF wavefunctions. I guess that similar ansatz are at work in the KS wavefunction, namely that spin-polarized calculations correspond to the use of unrestricted KS determinants.
It's not clear to me however how the magnetization constraint works in VASP. Specifically, when constraining the magnetization (NUPDOWN = #) does one use a restricted (eventually open-shell) or an unrestricted formulation?

Seemingly irrelevant, the question relates to the total spin-properties of system. Thus, for example, if my system has a triplet ground-state I can still access the singlet ground-state with a restricted calculation if M is forced to be 0, but I won't be able to get it in the unrestricted calculation (even forcing M=0).

Does anyone know how these options are implemented in VASP?

Thanks.

[support_vasp]

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