(2.2.25) Tozer : A feature of regular Kohn-Sham calculations using common exchange-correlation functionals is that the electronic energy does not in general equal the sum of the occupied orbital energies. Recently, proposed the direct energy Kohn-Sham (DEKS) scheme, whereby the Hartreeexchange-correlation potential is shifted by a constant, in order to make the electronic energy equal to the sum of the orbital energies. This shifted potential has attractive theoretical characteristics and so it is desirable to try to model it directly for use in DEKS calculations. The use of density-scaling homogeneity considerations is one possible way forward. 108 (2.2.26) Arbuznikov : The remarks of Schwerdtfeger in contribution (2.1.31) have prompted me to add a few words on relativistic exchange-correlation functionals.