Dear Robert, I am not familiar with the method for applying an exchange correlation. But is this applied by using perturbation on the Hamiltonian of the multi/electron system, that is a perturbation Hamiltonian which applied the effect from the exchange?
Subject: CCL: Exchange correlation
Date: Thu, 12 Jun 2014 21:31:49 -0400
No. The exchange refers to the energy penalty for anti-symmetrization of the wavefunction. It is a permutation operator (K) applied to the Coulomb operator (J). It is not enough to have Coulombic repulsion; QM dictates that no two fermions have the same quantum state. If you want to work with fermions, you have to represent a penalty toward having the same quantum state.
Correlation is an extended euphemism to mean "everything you do not get from the restrictions placed on the wavefunction in restricted Hartree-Fock theory." The term more precisely derives from the fact that the joint probability distribution function of the one-particle reduced density matrix shows that the there is no statistical correlation between two orbitals and their density...hence the term "correlation."
On 06/12/2014 07:05 PM, William McDonald pchem=-=ucsc.edu wrote: