# CCL: Exchange correlation

*From*: Víctor Luaña Cabal
<victor.^^^.fluor.quimica.uniovi.es>
*Subject*: CCL: Exchange correlation
*Date*: Fri, 13 Jun 2014 18:49:33 +0200

Sent to CCL by: =?iso-8859-1?Q?V=EDctor_Lua=F1a?= Cabal
[victor::fluor.quimica.uniovi.es]
On Thu, Jun 12, 2014 at 09:31:49PM -0400, Robert Molt Jr
r.molt.chemical.physics.**.gmail.com wrote:
> 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."
I absolutely agree with your position as it is the case of anybody that
has read anything coming from John C. Slater. However, it is the case
that the physicists in DF theory have createed their own pantheon and
Slater tends to be excluded.
So I'm afraid that the use of correlation or exchange-correlation
will continue to declare the different formation of two different
schools of people working on exactly the same field.
Best regards,
Dr. Víctor Luaña
--
\|/
|^.^|
+---!OO--\_/--OO!------------------------------+-----------------------
! Dr.Víctor Luaña !
! Departamento de Química Física y Analítica !
! Universidad de Oviedo, 33006-Oviedo, Spain !
! e-mail: victor**fluor.quimica.uniovi.es !
! phone: +34-985-103491 fax: +34-985-103125 !
+----------------------------------------------+
GroupPage : http://azufre.quimica.uniovi.es/ (being reworked)