Virial exchange energies from model exact-exchange potentials.
It is shown by the example of Slater's averaged exchange potential that a poor approximation to the optimized effective potential (OEP) can yield a deceptively accurate energy via the conventional Kohn-Sham energy functional. For a trial exchange potential to be correct, its Kohn-Sham energy must coincide with the value obtained by the Levy-Perdew virial relation. Significant discrepancies between Kohn-Sham and the virial exchange energies are found for self-consistent Slater, Becke-Johnson, and effective local potentials (ELPs); their relative magnitudes are used to argue that, as approximations to the exact-exchange OEP, ELPs are the most accurate. Virial energy discrepancies vanish for Yang-Wu OEPs when the orbital and auxiliary basis sets are balanced, and remain surprisingly small for oscillatory OEPs obtained with unbalanced basis sets.
Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada.
Alex P
AP
Gaiduk
Viktor N
VN
Staroverov