PROFASI
Version 1.5

Circular normal potential well. More...
#include <RestraintFunction.hh>
Public Member Functions  
int  set_pars (prf_xml::XML_Node *pars) 
Set parameters for circular normal potential.  
double  operator() (double x) 
Evaluate the function for a given value of the coordinate.  
double  estimate_max (double scale_large) 
Estimate a maximum based on some "large" scale.  
Public Member Functions inherited from prf::RestraintFunction  
RestraintFunction ()  
Default constructor.  
virtual double  estimate_min () 
Estimate a minimum.  
This is an adaptation of the circular normal or von Mises distribution for use as a potential well in angle space. The von Mises distribution is given by
where is the modified Bessel function. The parameter kappa
roughly corresponds to the inverse of the square of the width of the distribution. The angle in question does not appear in the denominator. It is therefore convenient to modify the function to :
This way of writing the function makes sure that the value is 0 when the the angle takes its mean value, and N when it is not. The user can choose the location (mu), width ( roughly inverse squareroot of kappa ) and the depth (N) of the potential well.

virtual 
The XML node passed should be a parameters
node with up to 3 child fields called kappa
, mean
and weight
in arbitrary order. Example:
<parameters> <mean>1.1342</mean> <kappa>8</kappa> <weight>10</weight> <parameters>
Reimplemented from prf::RestraintFunction.