"ChemCell WWW Site"_cws - "ChemCell Documentation"_cd - "ChemCell
Commands"_cc :c

:link(cws,http://www.cs.sandia.gov/~sjplimp/chemcell.html)
:link(cd,Manual.html)
:link(cc,Section_commands.html#comm)

:line

probability command :h3

[Syntax:]

probability style value :pre

style = {max} or {diff} :l
  {max} value = Pmax = fraction between 0.0 and 1.0
  {diff} value = M = multiplier on sum of diffusive distances :pre

[Examples:]

probability max 0.5
probability diff 1.5 :pre

[Description:]

Set parameters that determine how binary reactions are computed for
spatial simulations.  A binary reaction occurs in a timestep with a
probability P when a pair of reactant particles are within a cutoff
distance R.

The {max} style uses the specifed Pmax to set one distance R for all
reactions so that the fastest reaction (maximum rate constant) will
occur with probability Pmax and give the desired k for a well-mixed
system with diffusion-limited reactions.  Since other reactions happen
less frequently (smaller rate constants) their P values are set
smaller than the specified Pmax.

The {diff} style sets a distance R for each reaction based on the
diffusion coefficients of its 2 reactants.  The sum of the root-mean
squared value for each reactant is multipled by the specified M factor
to compute R.  The P for each reaction is then set so that each
reaction happens at the desired frequency for a well-mixed system with
diffusion-limitd reactions.

Note that values of P and R for individual reactions can be overridden
via the "react_modify"_react_modify.html command.

[Restrictions:]

This command can only be used for spatial simulations.

[Related commands:] none

[Default:]

max 0.5