[Pw_forum] spilling parameter in Lowdin - how to assign the charge that went into Nirvana ?

[degironc]

In order to calculate the spilling parameter with scaled atomic wfc's 
the easiest
way is to modify the atomic_wfc.f90 routine scaling the k+g vectors 
[arrays gk
and qg at the beginning of it] ... this is rather easy I think.
In order to optimize the scaling one needs to implement some 
minimization startegy...
this implies repeatedly calculate the spilling parameter (if using a 
method not requiring
gradients such as the simplex algorithm) or code the calculation of its 
derivatives if
one wants to use CG or similar algorithms.
stefano

Konstantin Kudin wrote:

> Hi all,
>
> Revisiting this month old topic, I'd like to ask how easy/difficult
>would it be to add the optimization of the atomic basis for the Lowdin
>charge evaluation?
>
> The optimization is described here:
>http://dx.doi.org/10.1016/0038-1098(95)00341-X
>
> With that, one could perhaps even calculate the spread of the atomic
>density, and figure out if the atom became larger/smaller as a result
>of chemical interaction.
>
> Thanks!
> Kostya
>
>
>--- Paolo Giannozzi <giannozz at nest.sns.it> wrote:
>
>  
>
>>On Mar 24, 2007, at 15:54 , Andrea Ferretti wrote:
>>
>>    
>>
>>>Lowding orbitals in Quantum-Espresso (at least as far as I know)
>>>      
>>>
>>are
>>    
>>
>>>computed from the atomic reference states from pseudopotential data
>>>according to:
>>>
>>>S_ij = < i | j >      are the overlaps of atomic orbitals i and j
>>>
>>>lowding orbitals are then obtained as
>>>| low_i > =  R_ij  | j >
>>>
>>>where  R = S^{-1/2}
>>>
>>>so I think there is no optimization (in the sense of the paper
>>>      
>>>
>>above)
>>    
>>
>>>but maybe I am missing something
>>>      
>>>
>>no, you aren't missing anything: the atomic basis is not optimized
>>
>>Paolo
>>---
>>Paolo Giannozzi, Democritos and University of Udine, Italy
>>
>>    
>>