[Pw_forum] About nelec and tot_charge again

[Paolo Giannozzi]

On Monday 24 December 2007 12:11, oulihui666 wrote:

> I intend to ask wheather I could add a extra electron and +1 charge
> simultaneously?

you can add an extra electron by setting variable "nelec" to the desired
charges. The code will automatically add a neutralizing background (it
must! the energy of a charged supercell is infinite). In practice, the energy
is calculated as usual, but the divergent terms will be calculated as if 
the system was neutral. For a molecule the energy so obtained will 
converge for increasing size of the supercell to the true energy of the
charged molecule; there are various tricks to speedup the convergence
(e.g. the Makov-Payne correction). Formation energies of charged defects
can also be calculated but it is a more tricky business.

By the way, all this has been explained 2n+1 times.

Paolo
-- 
Paolo Giannozzi, Democritos and Udine University