Mulliken population

[jerry]

Dear,
     I have calculated the Mulliken population of a water molecule according to the manual. I want to know that what does this population represent for? Can this represent the electron withdrawing or donating abilities of atoms or radicals?
    Thanks a lot!

Admin edit: Confusing spelling mistake in subject

[Anders Blom]

The Mulliken population is a rather crude measure of how many electrons are localized near a certain atom. Numerically it's well-defined, by physically it can on occasion be misleading (for instance, it can be negative in some cases). Still, it's a decent estimate of whether an atom attracts or repels electrons, in a certain situation, and (as usual is the case) differences can be trusted far better than absolute values.

[jerry]

I think the relative values of different atoms in a molecule represent their electron withdrawing or donating abilities. It is also the case for the comparison of diffrerft substituents in a molecule.

[Nordland]

The Mulliken population is projection of the density matrix onto the basis orbitals of the individual atoms.

The true question is that, can the Mulliken population be used to say something about a atoms electron negativity?

So what I have done, is that I run a calculation on H-O for a series of different basis set, and the conclusion
is that whatever setup, the oxygen orbitals ends up with the most electrons, so it supports the fact that Oxygen is
much more Electronegativity than Hydrogen.

[Nordland]

On a second note, the wikipedia has a good page on the matter http://en.wikipedia.org/wiki/Electronegativity

[jerry]

Very useful answers. Thanks a lot!