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How to simulate a potential barrier?

  1. Apr 25, 2008 #1

    I am doing simulations on a particle in some potential together with a fluctuating force and friction. To do that, I use the Langevin equation with the fluctuating force being a random number from a normal distribution with a temperature-dependent variance. I use a Verlet-algorithm for the calculation of position, velocity and acceleration (x,v and a) at each timestep.

    My problem is how I can implement a high potential barrier - basically a wall. What I tried so far was to change the sign of x and v once it happens that x<0 (I have the barrier at x=0, and a linear potential at x>0).

    But this gives unrealistic results, the particle goes way to far away from the barrier at very low temperatures - it looks like the particle in some way gets quite much energy when it hits the wall.

    Does anyone have some suggestion on how to implement such a barrier? Or help me explain why my current method fails?

    I can mention it probably isn't problems with the Verlet-algorithm itself or something else, since it yields very nice results if I use a harmonic potential.

    Let me know if you need more information :)
  2. jcsd
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