Kohn-Sham equations Kieron Burke University of California, Irvine (UCI) I will introduce the Kohn-Sham scheme. I will define the exchange-correlation energy and show the exact expression for the KS potential. I will discuss what the exact Exc functional does and does not do. I will discuss the question of v-representability. I will give the argument for the exact KS HOMO matching the ionization potential of a system.