# [MD] Lennard Jones

 P: 47 Hi For a simulation regarding Lennard Jones fluids I'm getting divergences. I have particles in a fixed volume. I calculate distances between these particles to find the force. However in the first iteration I already get divergences (NaN values in matlab). I use $$F_x^{ij} = 24\varepsilon \left( 2r_{ij}^{-14}-r_{ij}^{-8}\right)\cdot \Delta x_{ij}$$ Where the i,j have to do with the particles I'm viewing. For each direction I get such a force. But some of the particles get so close that this force and hence the acceleration effectively become infinity. My simulation obviously breaks down at this point. I tried changing the timestep, this doesn't do anything. It worked at some point but I don't recall changing anything after that. Except adding the thermostat code which I can turn off. The divergence remains. You can find my (messy) code in this pastebin http://pastebin.com/62v1yTCY I've been looking at it for hours already yet I can't find any solution. JorisL Edit; I had divergences before. Those were caused by an error in applying the periodic boundary conditions. I forgot using the nearest image convention at that time.