dispersion.bzz (Source) 

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# Lennard-Jones parameters
TARGET     = 500.0
EPSILON    = 150.0
 
# Neighbor data to LJ interaction vector
function lj_vector(rid, data) {
  return math.vec2.newp(lj_magnitude(data.distance, TARGET, EPSILON), data.azimuth)
}
 
# Lennard-Jones interaction magnitude
function lj_magnitude(dist, target, epsilon) {
  return -(epsilon / dist) * ((target / dist)^4 - (target / dist)^2)
}
 
# Accumulator of neighbor LJ interactions
function lj_sum(rid, data, accum) {
  return math.vec2.add(data, accum)
}
 
# Calculates and actuates the flocking interaction
function disperse() {
  # Calculate accumulator
  var accum = neighbors.map(lj_vector).reduce(lj_sum, math.vec2.new(0.0, 0.0))
  if(neighbors.count() > 0)
    math.vec2.scale(accum, 1.0 / neighbors.count())
  # Move according to vector
  goto(accum.x, accum.y)
}
 
# Executed at init time
function init() {
}
 
# Executed every time step
function step() {
  disperse()
}
 
# Execute at exit
function destroy() {
}