The ABINIT Users Mailing List ( CLOSED )

[Xavier Gonze <gonze@pcpm.ucl.ac.be>]

Griselda Garcia wrote:
> Dear ABINIT users,
>
> I am a new user and I would like to know how to calculate the parameter 
> boxcut. 

You should not compute it by yourself ...
It is printed in the output file, e.g. :

 getcut: wavevector=  0.0000  0.0000  0.0000  ngfft=  16  16  16
         ecut(hartree)=     10.000   => boxcut(ratio)=   2.09149


From the help file I found that "boxcut" is the smallest ratio of the
> fft box side to the G vector basis sphere diameter. So, my question is how 
> can I calculate these two numbers?
>
> I know that Ecut is 0.5*(2*Pi/(k+Gmax))^2 and from here I can deduce Gmax 
> using k=0. Is G vector basis sphere diameter equal to 2*Gmax?
>
> And what about fft box side? How estimate it?
>
> Thanks a lot!!
>
> Regards,
>
> Griselda Garcia
> Pontificia Universidad Catolica
> Santiago - Chile