cp2k COMBINE_COLVAR/FUNCTION define exponential form function

[Marcella Iannuzzi]

Dear Tao,

yes this is the right way, but please keep the same name of the variable in 
the expression of the FUNCTION as the one you assign with the keyword 
VARIABLES 

regards
Marcella


On Friday, January 20, 2017 at 5:19:28 AM UTC+1, Sun Tao wrote:
>
> Dear All:
>
> I am trying to set up some collective variables in cp2k. I need to 
> calculate the exponential-form value of a defined collective variable, 
> which is the distance between certain 2 atoms, the form is as the following:
>
> f = 1/{1 + exp([distance(i, j) - 0.5]/1.5)}
>
> Shall I define the CV as the following?
>
>   &SUBSYS
>     &COLVAR
>        &COMBINE_COLVAR
>           &COLVAR
>              &DISTANCE
>                 ATOMS 1 5
>
>              &END
>           &END COLVAR
>           FUNCTION 1/(1+exp((CV-0.5)/1.5))
>           VARIABLES CV1 
>           ERROR_LIMIT 1.0E-8
>        &END
>     &END
>
>    &END
>
>
>
> Or the correct form should be something else? Thanks ~
>
>
> Tao
>
>
>
>
>
>
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