The charge state(s) of a point defect can be understood from the exchanging of electrons between the defective region and an electron reservoir. For a hypothetical II-VI compound AB as illustrated in Figure , the creation of a B vacancy (V B ) for example leaves 2 electrons remaining, since B has 6 valence electrons. The charge state of V B is determined by whether the remaining 2 electrons are released to the electron reservoir, which we can understand using a Le Chatelier's Principle-like argument. If E F is a Northwestern University, Evanston, IL 60208. * E-mail: MichaelToriyama2024@u.northwestern.edu, jeff.snyder@northwestern.edu ) is near the conduction band, then the electron reservoir will be more densely populated with electrons. As a result, the 2 electrons will likely remain localized at the vacancy site, forming the V 0 B charged defect. (b) If E F is closer to the valence band, then the electron reservoir will be less densely populated, and the 2 electrons will likely delocalize from the vacancy site and join the electron reservoir. This will consequently form the V +2 B charged defect. The E F -dependent behavior of the electrons can also be described using molecular orbitals. If E F is near the conduction band and the 2 electrons are localized at the vacancy site as in (a), then this can be interpreted as the filling of a 2-electron molecular orbital state that exists below E F in energy, denoted "MO". If E F is near the valence band and the 2 electrons are delocalized from the vacancy site as in (b), then this can be interpreted as depleting the 2-electron MO state.