[DFTB-Plus-User] Fixed Charge Question

[Ben Hourahine]

Hello Mandelle,

experimentally even the most ionic material (LiF) does not have a charge
transfer large enough to give the formal picture of Li^+1 F^-1 ions.

But if you instead need the electrostatic energy of an array of charges
then the Madelung constant for the lattice should give this energy.

It is in principle possible to force DFTB+ to produce such an
un-physical charge transfer, however this is not the ground state of the
real system, it is instead equivalent to the system being in a (strong)
external field of some sort. If you do want to try this we can discuss
this off list.

Regards

Ben

Mandelle Danser wrote:
> I have a system that has one molecule as an anion and one as a cation.
>  I was hoping to have them start out in an MD simulation having charges
> that reflect this so that they can possibly interact the way they are
> predicted to.  Is this possible?
> Thank you.
> 

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     Dr. B. Hourahine, SUPA, Department of Physics,
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