Re: want to modify NDSolve--molecular dynamics with mathematica

*To*: mathgroup at smc.vnet.net*Subject*: [mg26365] Re: want to modify NDSolve--molecular dynamics with mathematica*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Wed, 13 Dec 2000 02:41:24 -0500 (EST)*Organization*: Universitaet Leipzig*References*: <90v82t$79m@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hi, you can write your equation with Mod[x[t],a0] but it will make the InterpolatingFunction[]s returned by NDSolve[] unusable. Because x[t] will jump back to for x>a0 and the interpolation is useless. You must write your own initial value solver. Regards Jens "Toshiyuki (Toshi) Meshii" wrote: > > 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

**Follow-Ups**:**Re: Re: want to modify NDSolve--molecular dynamics with mathematica***From:*Richard Gass <gass@physics.uc.edu>