want to modify NDSolve--molecular dynamics with mathematica

*To*: mathgroup at smc.vnet.net*Subject*: [mg26304] want to modify NDSolve--molecular dynamics with mathematica*From*: "Toshiyuki \(Toshi\) Meshii" <meshii at mech.fukui-u.ac.jp>*Date*: Sun, 10 Dec 2000 00:20:14 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Hello, I was wondering whether I can apply NDSolve to molecular dynamics, on the standpoint of periodical boundary condition. The eqation I want to solve is the simple Newton equation (Let me simplify the problem). m D[x, {x,2}] == F However, periodical boundary condition makes it difficult to apply NDSolve. That is, once 0<x[t]<a0 is not satisfied (a0 is a constant), I have to move the atom so that this condition is satisfied. In concrete, if x[t]<0 ---> x[t]=x[t]+a0 if x[t]>a0 ---> x[t]=x[t]-a0 and then restart to solve the equation. Is there any way to realize this by directly applying NDSolve? If not, how can I modify NDSolve? -Toshi