I am currently confused about anti-symmetrization of wavefunctions. In a thread "Still confused about super position and mixed state", kith responded that anti-symmetrization was not done thus the none of the bras and kets shows any properties of a possible state of a molecule I have mentioned in the thread OP. 1) So then how can it be done? The wavefunctions used in the problem has no information about what kind of equation it is composed of. So we have no way of knowing how to anti-symmetrize the wavefunctions. 2) Couldn't the wavefunctions used in the thread be considered as wavefunction that have already been antisymmetrized? Otherwise, quite some quantum chemical theories (such as spin-orbit coupling, excitonic interactions, ligand field, etc.) would fails because most textbooks and papers regarding these theory typically don't consider antisymmetrization or at least don't mention it. 3) Practically, how is anti-symmetrization done in general? It seems to me that anti-symmetrization is a tedious work considering how many electrons are included in a molecule. Both Antisymmetrizer and Slater determinants seems to be tons of work. Are there any way to come around this tremendous amount of work?