[DFTB-Plus-User] Dispersion model (SlaterKirkwood)

[Bálint Aradi]

On 12/19/2012 08:56 AM, 张超 wrote:
> Dear Ben,
> 
> Thank you for your answer.  Whether Slater-Kirkwood model  is more accurate than the UFF dispersion ?
> 
> 
> In addition, I do not know about that 'check for re-hybridization during the calculation'. What I need to do?
> The code about dispersion is as follows,
> 
> Dispersion = SlaterKirkwood{
>  PolarRadiusCharge =HybridDependentPol{
>   C={
>    CovalentRadius[Angstrom]=0.77
>     HybridPolarisations [Angstrom^3, Angstrom,]={
>     1.382 1.382 1.382 1.064 1.064 1.064 3.8 3.8 3.8 3.8 3.8 3.8 2.5
> }
> } 
> }
> }                  

 As long as you use the SlaterKirkwodd dispersion, there won't be any
update for the coordinations of the atoms. Even if the coordination
changes, you will use the dispersion constants for the initial
configuration. (This is not something you can change, we implemented it
this way to be compatible with old historical DFTB versions).

 The UFF is better in that regard. However, please note, that the UFF
model gives a constant repulsive term to all covalent bonds (see the
reference given in the manual), so that if you wanted to study for
example sp2/sp3 hibridization at high temperatures, it would somewhat
bias your system to sp2 hibridization.

  Best regards,

  Bálint


-- 
Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen
http://www.bccms.uni-bremen.de/cms/people/b_aradi/


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