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Quantum chemistry, Density functional theory, Exchange interactions, Adiabatic-connection formalism
Abstract:
The exchange-only virial relation due to Levy and Perdew is revisited. Invoking the adiabatic connection, we introduce the exchange energy in terms of the right-derivative of the universal density functional w.r.t. the coupling strength λ at λ = 0. This agrees with the Levy–Perdew definition of the exchange energy as a high-density limit of the full exchange–correlation energy. By relying on v-representability for a fixed density at varying coupling strength, we prove an exchange-only virial relation without an explicit local-exchange potential. Instead, the relation is in terms of a limit (λ ↘ 0) involving the exchange–correlation potential
[not displayable here], which exists by assumption of v-representability. On the other hand, a local-exchange potential vx is not warranted to exist as such a limit.
