# [molpro-user] Bug in calculation of expactation value of the potential energy operator (POT)

Evgeniy Gromov Evgeniy.Gromov at pci.uni-heidelberg.de
Thu Mar 26 08:51:23 GMT 2009

Dear Gerald,

give the expression for the potential energy operator
(POT) used to get the expectation value (if you know).
Thanks!

Best regards,
Evgeniy

Gerald Knizia wrote:
> On Wednesday 25 March 2009 16:02, Evgeniy Gromov wrote:
>> Dear Developers and Users of Molpro,
>>
>> There seems to be bug in calculation of expectation
>> value of the potential energy operator (POT). The
>> value I get is not equal to <E_total>-<E_kinetic>.
>> I mean it should be
>>
>> <E_potential>=<E_total>-<E_kinetic>
>>
>> shouldn't it?
>
> There are still the nuclear repulsion energy and the two electron repulsion
> energy. The total energy is:
> 	E_tot = <t> + <v_nuc> + E_nuc + <2e-terms>
> where:
> 	t is the electronic kinetic energy
> 	v_nuc is the energy due to the interaction of the atom cores
> 		with the electrons
> 	E_nuc = \sum_{a,b!=a} Z_a Z_b/||R_a-R_b|| is the electrostatic
> 		repulsion of the atom cores amongst themselves.
> 	2e-terms is the energy due to the interaction of the electrons with
> 		each other
> For RHF, the 2e-terms are again given by j + k, which are effective 1-particle
> operators representing the mean field Coulomb potential due to the electrons
> and Pauli repulsion (k=exchange operator). For general theories these
> 2e-terms look more complicated would require the 2-RDM for an exact
> evaluation as general property expectation value.

--
_______________________________________
Dr. Evgeniy Gromov
Theoretische Chemie
Physikalisch-Chemisches Institut
Im Neuenheimer Feld 229
D-69120 Heidelberg
Germany

Telefon: +49/(0)6221/545263
Fax: +49/(0)6221/545221
E-mail: evgeniy at pci.uni-heidelberg.de
_______________________________________