[CPMD-list] "True" Eigenvalues

[Ari P Seitsonen]

Dear Eung-Gun,

  I write what I know, some one please correct and add: In order to get the
correct eigenvalues you need to have the reference, that is, vacuum,
somewhere in your system. So you can have 2-dimensional (surface = slab
geometry), 1D (line) or 0D (isolated system). When you have performed your
calculation you check the value of the electro-static potential in the
(middle of) vacuum region, and subtract that from the eigenvalues.

    Greetings (again/still) from Zurich,

       apsi

-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
 Ari Paavo Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
 Tel +41 1 635 44 97 / Fax +41 1 635 68 38 / GSM +41 79 719 09 35      
 Anschrift: Physikalisch Chemisches Institut (PCI), Universität Zürich (UniZh)
 Indirizzo: Winterthurerstrasse 190, CH-8057 Zürich
 Address:   Schweiz / Svizzera / Suisse / Svizra / Switzerland

On Wed, 24 Nov 2004, Eung-Gun Kim wrote:

> Dear List Subscribers,
> 
> I was told that in most plane-wave/pseudopotential codes, there is a constant
> energy term dropped when eigenvalues are calculated.  For most purposes where
> only the energy difference matters, one would not need this dropped term.
> However, in
> some instances, for example, when one calculates the work function OR compares
> HOMO/LUMO levels between two different molecules, this dropped term is to be
> recovered.  Is there a way to retrieve this missing term to obtain "true"
> eigenvalues?  Thanks very much for reading.
> 
> Best regards,
> 
> EG Kim
> 
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