Hi, I'm wondering why polarization calculations cannot be performed when the system has an odd number of electrons. I've read through the derivations by Resta and the Berry phase approach, and while I follow along in a moderate sense I don't see how the requirement for an even number of electrons enters the picture. For example, the polarization of a single silver atom in void cannot be calculated, but a system of two silver atoms works fine.
Any comments much appreciated, Chris Rowan M.Sc. Candidate University of Victoria Canada
