how to determine the cutoff and exponent number in defining the coordination

[wangxi... at gmail.com]

Dear Cp2K users:

I am now trying to do some calculation following the reaction coordinate. 
In the definition of coordination, I don't quite understand how to 
determine the most suitable exponent number and cutoff in the equation. I 
have also read the articles of Spirk, 1998. In my understanding, the cutoff 
should be considered as the maximum distance for a efficient coordination 
from the central ion. Is it right? 

Secondly, the default exponent numbers nn and nd in the equation below are 
6, 12, respectively. For a specific system, how can we determine the 
exponent number nn and nd. Many thanks in advance.

[image: K73O$K)EGH1RC_8}86TCD at O.png] <about:invalid#zClosurez>
Xinyu
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